Weekdays repeat every seven days
2.NBT.A.2 · adapt
Part of a calendar for one month is shown. In this month, the 5th falls on a Saturday. What day of the week is the 26th?
Show solution
Understand
In a month's calendar the 5th is a Saturday. I need to find what day of the week the 26th is.
Givens
- The 5th of the month falls on a Saturday.
- Weekdays run Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday and then repeat.
Unknowns
- The weekday of the 26th.
Constraints
- The same weekday repeats every 7 days.
Plan
#5 Look for a Pattern · also uses: #1 Draw a Diagram
A calendar repeats its weekdays every 7 days, so the dates that share a column with the 5th are 5, 12, 19, 26. Spotting this skip-counting-by-7 pattern is faster than writing out every single day.
Execute
#5 Look for a Pattern 2.NBT.A.2
From the 5th to the 26th is 26 - 5 = 21 days later.
Subtracting to find how many days apart is a Grade 2 subtraction students can do.
#5 Look for a Pattern 2.NBT.A.2
21 days is exactly 3 weeks because 7 + 7 + 7 = 21 (skip-counting by 7). After any whole number of weeks the weekday is the same.
Skip-counting by 7 to land exactly on 21 shows the day lands in the same column.
#1 Draw a Diagram 2.NBT.A.2
Because 21 days is a whole 3 weeks, the 26th is the same weekday as the 5th. The 5th is Saturday, so the 26th is also Saturday. (The Saturday dates are 5, 12, 19, 26.)
Same column on the calendar means same weekday.
Answer: Saturday
Review
Listing the Saturdays from the 5th by adding 7 each time gives 5, 12, 19, 26 — the 26th appears, confirming it is a Saturday.
Draw the calendar grid and count forward 21 boxes from the 5th; you land in the same Saturday column.
Standards · min grade 2
2.NBT.A.2Count within 1000, skip-count by 5s, 10s, and 100s — Skip-counting by 7 (and subtracting) to see that 21 days is 3 whole weeks so the weekday repeats.
💡 This only needs the Grade 2 idea that weekdays repeat every 7 days, so dates 7 apart share a day!