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Find a future date using days per month · 8 practice problems

1.MD.B.3

Generated variants — 8

Freshly produced from the archetype’s parameters — problem, figure, and solution derived together.

Variant 1 answer: May 9

March has 31 days. Starting from March 25, 2025, what is the date 45 days later? Give the month and day.

(A knuckle mnemonic: months on the raised knuckles have 31 days; months in the dips between knuckles have 30 days. February is the short month.)

Jan Mar May Jul Aug Apr Jun Sep Nov Knuckles (raised): 31 days Dips (between): 30 days
Show solution

Understand

March has 31 days. Starting from March 25, 2025, find the date that is 45 days later (give month and day).

Givens
  • March has 31 days.
  • Start date is March 25, 2025.
  • We move forward 45 days.
  • The knuckle mnemonic in the figure tells which months have 30 or 31 days.
Unknowns
  • The month and day that is 45 days after March 25, 2025.
Constraints
  • Days roll over into the next month once a month's days run out.

Plan

#7 Identify Subproblems · also uses: #11 Work Backwards

Break the days into 'days left in the start month' plus 'days spilling into later months.' Subtract the start-month part, and count the rest forward using each month's day count. This keeps every month boundary clear.

Execute

#7 Identify Subproblems 1.MD.B.3
From March 25 to the end of March (March 31) is 31 minus 25 days.
31−25=631 - 25 = 6
March 25 plus 6 days lands exactly on the last day of March.
#7 Identify Subproblems 1.MD.B.3
Of the 45 days, 6 are used getting to the end of March. The remaining days fall into the following month(s).
45−6=3945 - 6 = 39
After landing on the last day of the start month, the leftover days are counted forward into the next month.
#11 Work Backwards 1.MD.B.3
Stepping the leftover 39 days forward from the last day of March, using each month's true length, lands on May 9.
end of March+39 days=May 9\text{end of }March + 39\text{ days} = \text{May 9}
Days roll into the next month once a month's days run out; keep going until the leftover days are used up.
Answer: May 9

Review

Counting forward 45 days from March 25, 2025, using each month's true length, lands on May 9, which is a valid date in its month.

Count by whole months: fill the start month to its last day, then add the remaining days month by month until the leftover runs out — same answer.

Standards · min grade 1

  • 1.MD.B.3 Tell and write time in hours and half-hours using analog and digital clocks — Working with calendar dates and days within months to find a future date.
💡 Use up the days left this month first, then count the rest into the next month: simple Grade 1 calendar counting!
Variant 2 answer: July 7

June has 30 days. Starting from June 12, 2024, what is the date 25 days later? Give the month and day.

(A knuckle mnemonic: months on the raised knuckles have 31 days; months in the dips between knuckles have 30 days. February is the short month.)

Jan Mar May Jul Aug Apr Jun Sep Nov Knuckles (raised): 31 days Dips (between): 30 days
Show solution

Understand

June has 30 days. Starting from June 12, 2024, find the date that is 25 days later (give month and day).

Givens
  • June has 30 days.
  • Start date is June 12, 2024.
  • We move forward 25 days.
  • The knuckle mnemonic in the figure tells which months have 30 or 31 days.
Unknowns
  • The month and day that is 25 days after June 12, 2024.
Constraints
  • Days roll over into the next month once a month's days run out.

Plan

#7 Identify Subproblems · also uses: #11 Work Backwards

Break the days into 'days left in the start month' plus 'days spilling into later months.' Subtract the start-month part, and count the rest forward using each month's day count. This keeps every month boundary clear.

Execute

#7 Identify Subproblems 1.MD.B.3
From June 12 to the end of June (June 30) is 30 minus 12 days.
30−12=1830 - 12 = 18
June 12 plus 18 days lands exactly on the last day of June.
#7 Identify Subproblems 1.MD.B.3
Of the 25 days, 18 are used getting to the end of June. The remaining days fall into the following month(s).
25−18=725 - 18 = 7
After landing on the last day of the start month, the leftover days are counted forward into the next month.
#11 Work Backwards 1.MD.B.3
Stepping the leftover 7 days forward from the last day of June, using each month's true length, lands on July 7.
end of June+7 days=July 7\text{end of }June + 7\text{ days} = \text{July 7}
Days roll into the next month once a month's days run out; keep going until the leftover days are used up.
Answer: July 7

Review

Counting forward 25 days from June 12, 2024, using each month's true length, lands on July 7, which is a valid date in its month.

Count by whole months: fill the start month to its last day, then add the remaining days month by month until the leftover runs out — same answer.

Standards · min grade 1

  • 1.MD.B.3 Tell and write time in hours and half-hours using analog and digital clocks — Working with calendar dates and days within months to find a future date.
💡 Use up the days left this month first, then count the rest into the next month: simple Grade 1 calendar counting!
Variant 3 answer: January 24

December has 31 days. Starting from December 20, 2024, what is the date 35 days later? Give the month and day.

(A knuckle mnemonic: months on the raised knuckles have 31 days; months in the dips between knuckles have 30 days. February is the short month.)

Jan Mar May Jul Aug Apr Jun Sep Nov Knuckles (raised): 31 days Dips (between): 30 days
Show solution

Understand

December has 31 days. Starting from December 20, 2024, find the date that is 35 days later (give month and day).

Givens
  • December has 31 days.
  • Start date is December 20, 2024.
  • We move forward 35 days.
  • The knuckle mnemonic in the figure tells which months have 30 or 31 days.
Unknowns
  • The month and day that is 35 days after December 20, 2024.
Constraints
  • Days roll over into the next month once a month's days run out.

Plan

#7 Identify Subproblems · also uses: #11 Work Backwards

Break the days into 'days left in the start month' plus 'days spilling into later months.' Subtract the start-month part, and count the rest forward using each month's day count. This keeps every month boundary clear.

Execute

#7 Identify Subproblems 1.MD.B.3
From December 20 to the end of December (December 31) is 31 minus 20 days.
31−20=1131 - 20 = 11
December 20 plus 11 days lands exactly on the last day of December.
#7 Identify Subproblems 1.MD.B.3
Of the 35 days, 11 are used getting to the end of December. The remaining days fall into the following month(s).
35−11=2435 - 11 = 24
After landing on the last day of the start month, the leftover days are counted forward into the next month.
#11 Work Backwards 1.MD.B.3
Stepping the leftover 24 days forward from the last day of December, using each month's true length, lands on January 24.
end of December+24 days=January 24\text{end of }December + 24\text{ days} = \text{January 24}
Days roll into the next month once a month's days run out; keep going until the leftover days are used up.
Answer: January 24

Review

Counting forward 35 days from December 20, 2024, using each month's true length, lands on January 24, which is a valid date in its month.

Count by whole months: fill the start month to its last day, then add the remaining days month by month until the leftover runs out — same answer.

Standards · min grade 1

  • 1.MD.B.3 Tell and write time in hours and half-hours using analog and digital clocks — Working with calendar dates and days within months to find a future date.
💡 Use up the days left this month first, then count the rest into the next month: simple Grade 1 calendar counting!
Variant 4 answer: January 4

November has 30 days. Starting from November 5, 2025, what is the date 60 days later? Give the month and day.

(A knuckle mnemonic: months on the raised knuckles have 31 days; months in the dips between knuckles have 30 days. February is the short month.)

Jan Mar May Jul Aug Apr Jun Sep Nov Knuckles (raised): 31 days Dips (between): 30 days
Show solution

Understand

November has 30 days. Starting from November 5, 2025, find the date that is 60 days later (give month and day).

Givens
  • November has 30 days.
  • Start date is November 5, 2025.
  • We move forward 60 days.
  • The knuckle mnemonic in the figure tells which months have 30 or 31 days.
Unknowns
  • The month and day that is 60 days after November 5, 2025.
Constraints
  • Days roll over into the next month once a month's days run out.

Plan

#7 Identify Subproblems · also uses: #11 Work Backwards

Break the days into 'days left in the start month' plus 'days spilling into later months.' Subtract the start-month part, and count the rest forward using each month's day count. This keeps every month boundary clear.

Execute

#7 Identify Subproblems 1.MD.B.3
From November 5 to the end of November (November 30) is 30 minus 5 days.
30−5=2530 - 5 = 25
November 5 plus 25 days lands exactly on the last day of November.
#7 Identify Subproblems 1.MD.B.3
Of the 60 days, 25 are used getting to the end of November. The remaining days fall into the following month(s).
60−25=3560 - 25 = 35
After landing on the last day of the start month, the leftover days are counted forward into the next month.
#11 Work Backwards 1.MD.B.3
Stepping the leftover 35 days forward from the last day of November, using each month's true length, lands on January 4.
end of November+35 days=January 4\text{end of }November + 35\text{ days} = \text{January 4}
Days roll into the next month once a month's days run out; keep going until the leftover days are used up.
Answer: January 4

Review

Counting forward 60 days from November 5, 2025, using each month's true length, lands on January 4, which is a valid date in its month.

Count by whole months: fill the start month to its last day, then add the remaining days month by month until the leftover runs out — same answer.

Standards · min grade 1

  • 1.MD.B.3 Tell and write time in hours and half-hours using analog and digital clocks — Working with calendar dates and days within months to find a future date.
💡 Use up the days left this month first, then count the rest into the next month: simple Grade 1 calendar counting!
Variant 5 answer: November 6

August has 31 days. Starting from August 8, 2025, what is the date 90 days later? Give the month and day.

(A knuckle mnemonic: months on the raised knuckles have 31 days; months in the dips between knuckles have 30 days. February is the short month.)

Jan Mar May Jul Aug Apr Jun Sep Nov Knuckles (raised): 31 days Dips (between): 30 days
Show solution

Understand

August has 31 days. Starting from August 8, 2025, find the date that is 90 days later (give month and day).

Givens
  • August has 31 days.
  • Start date is August 8, 2025.
  • We move forward 90 days.
  • The knuckle mnemonic in the figure tells which months have 30 or 31 days.
Unknowns
  • The month and day that is 90 days after August 8, 2025.
Constraints
  • Days roll over into the next month once a month's days run out.

Plan

#7 Identify Subproblems · also uses: #11 Work Backwards

Break the days into 'days left in the start month' plus 'days spilling into later months.' Subtract the start-month part, and count the rest forward using each month's day count. This keeps every month boundary clear.

Execute

#7 Identify Subproblems 1.MD.B.3
From August 8 to the end of August (August 31) is 31 minus 8 days.
31−8=2331 - 8 = 23
August 8 plus 23 days lands exactly on the last day of August.
#7 Identify Subproblems 1.MD.B.3
Of the 90 days, 23 are used getting to the end of August. The remaining days fall into the following month(s).
90−23=6790 - 23 = 67
After landing on the last day of the start month, the leftover days are counted forward into the next month.
#11 Work Backwards 1.MD.B.3
Stepping the leftover 67 days forward from the last day of August, using each month's true length, lands on November 6.
end of August+67 days=November 6\text{end of }August + 67\text{ days} = \text{November 6}
Days roll into the next month once a month's days run out; keep going until the leftover days are used up.
Answer: November 6

Review

Counting forward 90 days from August 8, 2025, using each month's true length, lands on November 6, which is a valid date in its month.

Count by whole months: fill the start month to its last day, then add the remaining days month by month until the leftover runs out — same answer.

Standards · min grade 1

  • 1.MD.B.3 Tell and write time in hours and half-hours using analog and digital clocks — Working with calendar dates and days within months to find a future date.
💡 Use up the days left this month first, then count the rest into the next month: simple Grade 1 calendar counting!
Variant 6 answer: May 30

April has 30 days. Starting from April 10, 2024, what is the date 50 days later? Give the month and day.

(A knuckle mnemonic: months on the raised knuckles have 31 days; months in the dips between knuckles have 30 days. February is the short month.)

Jan Mar May Jul Aug Apr Jun Sep Nov Knuckles (raised): 31 days Dips (between): 30 days
Show solution

Understand

April has 30 days. Starting from April 10, 2024, find the date that is 50 days later (give month and day).

Givens
  • April has 30 days.
  • Start date is April 10, 2024.
  • We move forward 50 days.
  • The knuckle mnemonic in the figure tells which months have 30 or 31 days.
Unknowns
  • The month and day that is 50 days after April 10, 2024.
Constraints
  • Days roll over into the next month once a month's days run out.

Plan

#7 Identify Subproblems · also uses: #11 Work Backwards

Break the days into 'days left in the start month' plus 'days spilling into later months.' Subtract the start-month part, and count the rest forward using each month's day count. This keeps every month boundary clear.

Execute

#7 Identify Subproblems 1.MD.B.3
From April 10 to the end of April (April 30) is 30 minus 10 days.
30−10=2030 - 10 = 20
April 10 plus 20 days lands exactly on the last day of April.
#7 Identify Subproblems 1.MD.B.3
Of the 50 days, 20 are used getting to the end of April. The remaining days fall into the following month(s).
50−20=3050 - 20 = 30
After landing on the last day of the start month, the leftover days are counted forward into the next month.
#11 Work Backwards 1.MD.B.3
Stepping the leftover 30 days forward from the last day of April, using each month's true length, lands on May 30.
end of April+30 days=May 30\text{end of }April + 30\text{ days} = \text{May 30}
Days roll into the next month once a month's days run out; keep going until the leftover days are used up.
Answer: May 30

Review

Counting forward 50 days from April 10, 2024, using each month's true length, lands on May 30, which is a valid date in its month.

Count by whole months: fill the start month to its last day, then add the remaining days month by month until the leftover runs out — same answer.

Standards · min grade 1

  • 1.MD.B.3 Tell and write time in hours and half-hours using analog and digital clocks — Working with calendar dates and days within months to find a future date.
💡 Use up the days left this month first, then count the rest into the next month: simple Grade 1 calendar counting!
Variant 7 answer: August 19

July has 31 days. Starting from July 20, 2024, what is the date 30 days later? Give the month and day.

(A knuckle mnemonic: months on the raised knuckles have 31 days; months in the dips between knuckles have 30 days. February is the short month.)

Jan Mar May Jul Aug Apr Jun Sep Nov Knuckles (raised): 31 days Dips (between): 30 days
Show solution

Understand

July has 31 days. Starting from July 20, 2024, find the date that is 30 days later (give month and day).

Givens
  • July has 31 days.
  • Start date is July 20, 2024.
  • We move forward 30 days.
  • The knuckle mnemonic in the figure tells which months have 30 or 31 days.
Unknowns
  • The month and day that is 30 days after July 20, 2024.
Constraints
  • Days roll over into the next month once a month's days run out.

Plan

#7 Identify Subproblems · also uses: #11 Work Backwards

Break the days into 'days left in the start month' plus 'days spilling into later months.' Subtract the start-month part, and count the rest forward using each month's day count. This keeps every month boundary clear.

Execute

#7 Identify Subproblems 1.MD.B.3
From July 20 to the end of July (July 31) is 31 minus 20 days.
31−20=1131 - 20 = 11
July 20 plus 11 days lands exactly on the last day of July.
#7 Identify Subproblems 1.MD.B.3
Of the 30 days, 11 are used getting to the end of July. The remaining days fall into the following month(s).
30−11=1930 - 11 = 19
After landing on the last day of the start month, the leftover days are counted forward into the next month.
#11 Work Backwards 1.MD.B.3
Stepping the leftover 19 days forward from the last day of July, using each month's true length, lands on August 19.
end of July+19 days=August 19\text{end of }July + 19\text{ days} = \text{August 19}
Days roll into the next month once a month's days run out; keep going until the leftover days are used up.
Answer: August 19

Review

Counting forward 30 days from July 20, 2024, using each month's true length, lands on August 19, which is a valid date in its month.

Count by whole months: fill the start month to its last day, then add the remaining days month by month until the leftover runs out — same answer.

Standards · min grade 1

  • 1.MD.B.3 Tell and write time in hours and half-hours using analog and digital clocks — Working with calendar dates and days within months to find a future date.
💡 Use up the days left this month first, then count the rest into the next month: simple Grade 1 calendar counting!
Variant 8 answer: February 24

January has 31 days. Starting from January 15, 2024, what is the date 40 days later? Give the month and day.

(A knuckle mnemonic: months on the raised knuckles have 31 days; months in the dips between knuckles have 30 days. February is the short month.)

Jan Mar May Jul Aug Apr Jun Sep Nov Knuckles (raised): 31 days Dips (between): 30 days
Show solution

Understand

January has 31 days. Starting from January 15, 2024, find the date that is 40 days later (give month and day).

Givens
  • January has 31 days.
  • Start date is January 15, 2024.
  • We move forward 40 days.
  • The knuckle mnemonic in the figure tells which months have 30 or 31 days.
Unknowns
  • The month and day that is 40 days after January 15, 2024.
Constraints
  • Days roll over into the next month once a month's days run out.

Plan

#7 Identify Subproblems · also uses: #11 Work Backwards

Break the days into 'days left in the start month' plus 'days spilling into later months.' Subtract the start-month part, and count the rest forward using each month's day count. This keeps every month boundary clear.

Execute

#7 Identify Subproblems 1.MD.B.3
From January 15 to the end of January (January 31) is 31 minus 15 days.
31−15=1631 - 15 = 16
January 15 plus 16 days lands exactly on the last day of January.
#7 Identify Subproblems 1.MD.B.3
Of the 40 days, 16 are used getting to the end of January. The remaining days fall into the following month(s).
40−16=2440 - 16 = 24
After landing on the last day of the start month, the leftover days are counted forward into the next month.
#11 Work Backwards 1.MD.B.3
Stepping the leftover 24 days forward from the last day of January, using each month's true length, lands on February 24.
end of January+24 days=February 24\text{end of }January + 24\text{ days} = \text{February 24}
Days roll into the next month once a month's days run out; keep going until the leftover days are used up.
Answer: February 24

Review

Counting forward 40 days from January 15, 2024, using each month's true length, lands on February 24, which is a valid date in its month.

Count by whole months: fill the start month to its last day, then add the remaining days month by month until the leftover runs out — same answer.

Standards · min grade 1

  • 1.MD.B.3 Tell and write time in hours and half-hours using analog and digital clocks — Working with calendar dates and days within months to find a future date.
💡 Use up the days left this month first, then count the rest into the next month: simple Grade 1 calendar counting!