Set up an expression and compute in order · 12 practice problems

Understand

Each of 25 students gets one eraser ($0.60) and one pair of scissors ($0.65). Find the total cost for all the erasers and all the scissors together.

Plan

#7 Identify Subproblems · also uses: #8 Analyze the Units

Each student's cost is one small subproblem (eraser + scissors). Find the cost for one student, then multiply by 25. Tracking dollars keeps the arithmetic honest.

Execute

Review

Each student costs about $2, and$2 times 25 is about $50. Our exact answer$31.25 is close to that estimate, so it is reasonable.

Compute the two totals separately: 25 erasers cost $\$0.60 \times 25 = \$15.00$ and 25 pairs of scissors cost $\$0.65 \times 25 = \$16.25$; their sum is $31.25.

Standards · min grade 3

• 3.OA.A.3 Solve multiplication and division word problems within 100 — Multiplying the per-student cost by the number of students.
• 3.NBT.A.2 Fluently add and subtract within 1000 — Adding the eraser and scissors prices for one student.

Understand

Each of 40 students gets one eraser ($0.50) and one pair of scissors ($0.45). Find the total cost for all the erasers and all the scissors together.

Plan

#7 Identify Subproblems · also uses: #8 Analyze the Units

Each student's cost is one small subproblem (eraser + scissors). Find the cost for one student, then multiply by 40. Tracking dollars keeps the arithmetic honest.

Execute

Review

Each student costs about $1, and$1 times 40 is about $40. Our exact answer$38.00 is close to that estimate, so it is reasonable.

Compute the two totals separately: 40 erasers cost $\$0.50 \times 40 = \$20.00$ and 40 pairs of scissors cost $\$0.45 \times 40 = \$18.00$; their sum is $38.00.

Standards · min grade 3

• 3.OA.A.3 Solve multiplication and division word problems within 100 — Multiplying the per-student cost by the number of students.
• 3.NBT.A.2 Fluently add and subtract within 1000 — Adding the eraser and scissors prices for one student.

Understand

Each of 20 students gets one eraser ($0.75) and one pair of scissors ($0.80). Find the total cost for all the erasers and all the scissors together.

Plan

#7 Identify Subproblems · also uses: #8 Analyze the Units

Each student's cost is one small subproblem (eraser + scissors). Find the cost for one student, then multiply by 20. Tracking dollars keeps the arithmetic honest.

Execute

Review

Each student costs about $2, and$2 times 20 is about $40. Our exact answer$31.00 is close to that estimate, so it is reasonable.

Compute the two totals separately: 20 erasers cost $\$0.75 \times 20 = \$15.00$ and 20 pairs of scissors cost $\$0.80 \times 20 = \$16.00$; their sum is $31.00.

Standards · min grade 3

• 3.OA.A.3 Solve multiplication and division word problems within 100 — Multiplying the per-student cost by the number of students.
• 3.NBT.A.2 Fluently add and subtract within 1000 — Adding the eraser and scissors prices for one student.

Understand

Each of 50 students gets one eraser ($0.35) and one pair of scissors ($0.65). Find the total cost for all the erasers and all the scissors together.

Plan

#7 Identify Subproblems · also uses: #8 Analyze the Units

Each student's cost is one small subproblem (eraser + scissors). Find the cost for one student, then multiply by 50. Tracking dollars keeps the arithmetic honest.

Execute

Review

Each student costs about $1, and$1 times 50 is about $50. Our exact answer$50.00 is close to that estimate, so it is reasonable.

Compute the two totals separately: 50 erasers cost $\$0.35 \times 50 = \$17.50$ and 50 pairs of scissors cost $\$0.65 \times 50 = \$32.50$; their sum is $50.00.

Standards · min grade 3

• 3.OA.A.3 Solve multiplication and division word problems within 100 — Multiplying the per-student cost by the number of students.
• 3.NBT.A.2 Fluently add and subtract within 1000 — Adding the eraser and scissors prices for one student.

Understand

Each of 15 students gets one eraser ($1.20) and one pair of scissors ($1.30). Find the total cost for all the erasers and all the scissors together.

Plan

#7 Identify Subproblems · also uses: #8 Analyze the Units

Each student's cost is one small subproblem (eraser + scissors). Find the cost for one student, then multiply by 15. Tracking dollars keeps the arithmetic honest.

Execute

Review

Each student costs about $3, and$3 times 15 is about $45. Our exact answer$37.50 is close to that estimate, so it is reasonable.

Compute the two totals separately: 15 erasers cost $\$1.20 \times 15 = \$18.00$ and 15 pairs of scissors cost $\$1.30 \times 15 = \$19.50$; their sum is $37.50.

Standards · min grade 3

• 3.OA.A.3 Solve multiplication and division word problems within 100 — Multiplying the per-student cost by the number of students.
• 3.NBT.A.2 Fluently add and subtract within 1000 — Adding the eraser and scissors prices for one student.

Understand

Each of 30 students gets one eraser ($0.40) and one pair of scissors ($0.55). Find the total cost for all the erasers and all the scissors together.

Plan

#7 Identify Subproblems · also uses: #8 Analyze the Units

Each student's cost is one small subproblem (eraser + scissors). Find the cost for one student, then multiply by 30. Tracking dollars keeps the arithmetic honest.

Execute

Review

Each student costs about $1, and$1 times 30 is about $30. Our exact answer$28.50 is close to that estimate, so it is reasonable.

Compute the two totals separately: 30 erasers cost $\$0.40 \times 30 = \$12.00$ and 30 pairs of scissors cost $\$0.55 \times 30 = \$16.50$; their sum is $28.50.

Standards · min grade 3

• 3.OA.A.3 Solve multiplication and division word problems within 100 — Multiplying the per-student cost by the number of students.
• 3.NBT.A.2 Fluently add and subtract within 1000 — Adding the eraser and scissors prices for one student.

Understand

Each of 30 students gets one eraser ($0.90) and one pair of scissors ($0.95). Find the total cost for all the erasers and all the scissors together.

Plan

#7 Identify Subproblems · also uses: #8 Analyze the Units

Each student's cost is one small subproblem (eraser + scissors). Find the cost for one student, then multiply by 30. Tracking dollars keeps the arithmetic honest.

Execute

Review

Each student costs about $2, and$2 times 30 is about $60. Our exact answer$55.50 is close to that estimate, so it is reasonable.

Compute the two totals separately: 30 erasers cost $\$0.90 \times 30 = \$27.00$ and 30 pairs of scissors cost $\$0.95 \times 30 = \$28.50$; their sum is $55.50.

Standards · min grade 3

• 3.OA.A.3 Solve multiplication and division word problems within 100 — Multiplying the per-student cost by the number of students.
• 3.NBT.A.2 Fluently add and subtract within 1000 — Adding the eraser and scissors prices for one student.

Understand

Each of 32 students gets one eraser ($0.25) and one pair of scissors ($0.75). Find the total cost for all the erasers and all the scissors together.

Plan

#7 Identify Subproblems · also uses: #8 Analyze the Units

Each student's cost is one small subproblem (eraser + scissors). Find the cost for one student, then multiply by 32. Tracking dollars keeps the arithmetic honest.

Execute

Review

Each student costs about $1, and$1 times 32 is about $32. Our exact answer$32.00 is close to that estimate, so it is reasonable.

Compute the two totals separately: 32 erasers cost $\$0.25 \times 32 = \$8.00$ and 32 pairs of scissors cost $\$0.75 \times 32 = \$24.00$; their sum is $32.00.

Standards · min grade 3

• 3.OA.A.3 Solve multiplication and division word problems within 100 — Multiplying the per-student cost by the number of students.
• 3.NBT.A.2 Fluently add and subtract within 1000 — Adding the eraser and scissors prices for one student.

Understand

Each of 35 students gets one eraser ($0.70) and one pair of scissors ($0.80). Find the total cost for all the erasers and all the scissors together.

Plan

#7 Identify Subproblems · also uses: #8 Analyze the Units

Each student's cost is one small subproblem (eraser + scissors). Find the cost for one student, then multiply by 35. Tracking dollars keeps the arithmetic honest.

Execute

Review

Each student costs about $2, and$2 times 35 is about $70. Our exact answer$52.50 is close to that estimate, so it is reasonable.

Compute the two totals separately: 35 erasers cost $\$0.70 \times 35 = \$24.50$ and 35 pairs of scissors cost $\$0.80 \times 35 = \$28.00$; their sum is $52.50.

Standards · min grade 3

• 3.OA.A.3 Solve multiplication and division word problems within 100 — Multiplying the per-student cost by the number of students.
• 3.NBT.A.2 Fluently add and subtract within 1000 — Adding the eraser and scissors prices for one student.

Understand

Each of 28 students gets one eraser ($1.10) and one pair of scissors ($0.90). Find the total cost for all the erasers and all the scissors together.

Plan

#7 Identify Subproblems · also uses: #8 Analyze the Units

Each student's cost is one small subproblem (eraser + scissors). Find the cost for one student, then multiply by 28. Tracking dollars keeps the arithmetic honest.

Execute

Review

Each student costs about $2, and$2 times 28 is about $56. Our exact answer$56.00 is close to that estimate, so it is reasonable.

Compute the two totals separately: 28 erasers cost $\$1.10 \times 28 = \$30.80$ and 28 pairs of scissors cost $\$0.90 \times 28 = \$25.20$; their sum is $56.00.

Standards · min grade 3

• 3.OA.A.3 Solve multiplication and division word problems within 100 — Multiplying the per-student cost by the number of students.
• 3.NBT.A.2 Fluently add and subtract within 1000 — Adding the eraser and scissors prices for one student.

Understand

Each of 24 students gets one eraser ($0.85) and one pair of scissors ($0.90). Find the total cost for all the erasers and all the scissors together.

Plan

#7 Identify Subproblems · also uses: #8 Analyze the Units

Each student's cost is one small subproblem (eraser + scissors). Find the cost for one student, then multiply by 24. Tracking dollars keeps the arithmetic honest.

Execute

Review

Each student costs about $2, and$2 times 24 is about $48. Our exact answer$42.00 is close to that estimate, so it is reasonable.

Compute the two totals separately: 24 erasers cost $\$0.85 \times 24 = \$20.40$ and 24 pairs of scissors cost $\$0.90 \times 24 = \$21.60$; their sum is $42.00.

Standards · min grade 3

• 3.OA.A.3 Solve multiplication and division word problems within 100 — Multiplying the per-student cost by the number of students.
• 3.NBT.A.2 Fluently add and subtract within 1000 — Adding the eraser and scissors prices for one student.

Understand

Each of 20 students gets one eraser ($0.95) and one pair of scissors ($1.05). Find the total cost for all the erasers and all the scissors together.

Plan

#7 Identify Subproblems · also uses: #8 Analyze the Units

Each student's cost is one small subproblem (eraser + scissors). Find the cost for one student, then multiply by 20. Tracking dollars keeps the arithmetic honest.

Execute

Review

Each student costs about $2, and$2 times 20 is about $40. Our exact answer$40.00 is close to that estimate, so it is reasonable.

Compute the two totals separately: 20 erasers cost $\$0.95 \times 20 = \$19.00$ and 20 pairs of scissors cost $\$1.05 \times 20 = \$21.00$; their sum is $40.00.

Standards · min grade 3

• 3.OA.A.3 Solve multiplication and division word problems within 100 — Multiplying the per-student cost by the number of students.
• 3.NBT.A.2 Fluently add and subtract within 1000 — Adding the eraser and scissors prices for one student.