Topic Review Solutions — Decimals

Answers

1. Multiply decimals Fluency

   1. 13.5
   2. 16.8
   3. 1.8
   4. 1.8
   5. 0.63
   6. 6.0

2. Divide decimals Fluency

   1. 2.1
   2. 3.1
   3. 4
   4. 18
   5. 5
   6. 3.3

3. Rounding Fluency

   1. 3.75
   2. 12.4
   3. 0.057
   4. 10.00

4. Powers of ten Fluency

   1. 3470
   2. 0.506
   3. 80
   4. 720
   5. 0.63
   6. 450

5. Best buy Understanding

   1. Cereal A = 0.84 c/g; Cereal B = 0.78 c/g — Cereal B is the better buy
   2. Shampoo X = 2.3 c/mL; Shampoo Y = 2.2 c/mL — Shampoo Y is the better buy

6. Mia’s earnings Problem Solving

   1. $159.90
   2. $116.85
   3. $276.75
   4. $238.28

7. Add and subtract decimals Fluency

   1. 21.05
   2. 15.27
   3. 9.75
   4. 36.52

8. Estimate then calculate Understanding

   1. Estimate: 4 × 4 = 16; actual: 15.96
   2. Estimate: 20 ÷ 4 = 5; actual: 4.9
   3. 2.3 × 1.5 ≈ 2 × 2 = 4, so the answer must be close to 3–4, not 34.5. The student forgot to account for decimal places when multiplying.

9. Cheese comparison Understanding

   1. $12.60 ÷ 15 = $0.84 per 100 g
   2. $0.84 × 4 = $3.36
   3. Second cheese: $3.80 ÷ 2 = $1.90 per 100 g. First cheese ($0.84/100 g) is much better value.

10. Order from smallest to largest Fluency

    1. 0.405, 0.45, 0.504, 0.54
    2. 1.006, 1.06, 1.066, 1.6