ANSWER KEYS - Teacher Use Only

Multiplying Decimals | Grade 5

Student Concept Worksheet Answers
1
14
3.5 x 4: 35 x 4 = 140. 3.5 has 1 decimal place + 4 has 0 = 1 decimal place. Answer: 14.0 = 14
2
3.00 or 3
2.5 x 1.2: 25 x 12 = 300. 2.5 has 1 + 1.2 has 1 = 2 decimal places. Answer: 3.00 = 3
3
0.63
0.7 x 0.9: 7 x 9 = 63. 0.7 has 1 + 0.9 has 1 = 2 decimal places. Answer: 0.63
4
$9.40
$2.35 x 4: 235 x 4 = 940. 2.35 has 2 + 4 has 0 = 2 decimal places. Answer: $9.40
Practice Worksheet Answers

Part A: Decimal x Whole Number

# Problem Answer Work
14.3 x 521.543 x 5 = 215; 1 decimal place
26.25 x 425625 x 4 = 2500; 2 decimal places = 25.00
30.8 x 75.68 x 7 = 56; 1 decimal place
412.5 x 8100125 x 8 = 1000; 1 decimal place = 100.0

Part B: Decimal x Decimal

# Problem Answer Work
52.4 x 3.58.424 x 35 = 840; 2 decimal places
61.8 x 4.27.5618 x 42 = 756; 2 decimal places
70.6 x 0.50.30 or 0.36 x 5 = 30; 2 decimal places
83.25 x 0.41.3325 x 4 = 1300; 3 decimal places = 1.300

Part C: Mixed Practice

# Problem Answer
95.6 x 316.8
100.9 x 0.80.72
114.5 x 2.29.9

Part D: Word Problems

12
$10.50
$1.75 x 6 = $10.50 (175 x 6 = 1050; 2 decimal places)
13
12.6 square meters
4.5 x 2.8 = 12.60 = 12.6 (45 x 28 = 1260; 2 decimal places)
14
3.75 miles
0.75 x 5 = 3.75 (75 x 5 = 375; 2 decimal places)

Challenge Questions:

#15: Carlos is correct. 0.5 x 0.5 = 0.25. Maria is wrong because when you multiply two numbers that are both less than 1, the product is SMALLER than either factor. Think of it as "half of a half" = one quarter.

#16: 4.5 x 1.1 is greater. When you multiply by a number greater than 1, the product is greater than the original number. When you multiply by a number less than 1, the product is less than the original number. Since 1.1 > 1 and 0.9 < 1, multiplying by 1.1 gives a larger result.

FAST Practice Quiz Answers
1
A) 17
34 x 5 = 170. 3.4 has 1 decimal place, 5 has 0. Total: 1 decimal place. Answer: 17.0 = 17
2
D) 3.50 (also written as 3.5)
25 x 14 = 350. 2.5 has 1 + 1.4 has 1 = 2 decimal places. Answer: 3.50
3
B) 0.42
6 x 7 = 42. 0.6 has 1 + 0.7 has 1 = 2 decimal places. Answer: 0.42
4
Select: 3.6 x 2, 2.4 x 3, 0.9 x 8, and 1.2 x 6
3.6 x 2 = 7.2
2.4 x 3 = 7.2
0.9 x 8 = 7.2
1.2 x 6 = 7.2
0.8 x 0.9 = 0.72 (NOT 7.2)
5
B) $11.00
$2.75 x 4: 275 x 4 = 1100. 2 decimal places. Answer: $11.00
6
A) 17.6 square meters
5.5 x 3.2: 55 x 32 = 1760. 1 + 1 = 2 decimal places. Answer: 17.60 = 17.6 square meters
FAST Quiz Scoring Guide
Score Interpretation Recommended Action
6/6 Mastery Ready for dividing decimals. Challenge with multi-step problems and estimation.
4-5/6 Approaching Mastery Review decimal placement. Practice counting decimal places in both factors.
2-3/6 Developing Reteach with emphasis on the rule: count decimal places in BOTH numbers. Use money contexts.
0-1/6 Needs Intervention Small group instruction. Review whole number multiplication first, then introduce decimal placement step-by-step.
FAST Success Kit | Grade 5 | FL B.E.S.T. Standard: MA.5.NSO.2.5 | Answer Key - Teacher Use Only