Worked Example 1
Estimating a Product
3.9 × 4.2
- 1Round each factor: 3.9 ≈ 4 and 4.2 ≈ 4.
- 24 × 4 = 16.
- 3The exact answer (16.38) is close to 16.
Answer: about 16
Florida Grade 5 Math · Number Sense and Operations
MA.5.NSO.2.4: Estimating decimal multiplication and division
What this Grade 5 benchmark means, worked examples, common mistakes, and a free printable worksheet.
Created by a Florida mom · Published by Tropical Learning LLC
What Is Benchmark MA.5.NSO.2.4?
In Grade 5, students explore multiplying and dividing decimals to the hundredths using estimation, rounding, and place value, before learning the full procedures in Grade 6.
The key idea: round to friendly whole numbers to predict the answer, then use that estimate to place the decimal point and check whether a result makes sense.
Official benchmarkExplore the multiplication and division of multi-digit numbers with decimals to the hundredths using estimation, rounding and place value.
On the FAST test: part of the Grade 5 reporting category Number Sense and Operations with Fractions and Decimals, which is about 23–29% of the test.
Worked Examples
Worked Example 2
Placing the Decimal Point
4.5 × 2.1 = 945 (decimal missing)
- 1Estimate: 4.5 × 2.1 ≈ 5 × 2 = 10.
- 2The digits are 945. Which placement is close to 10: 0.945, 9.45, or 94.5?
- 39.45 is close to 10.
Answer: 9.45
Common Mistakes to Watch For
Placing the decimal point by guessing
Wrong:4.5 × 2.1 = 94.5
Estimate first: about 5 × 2 = 10. So the answer must be 9.45, not 94.5.
Thinking multiplying always makes a number bigger
Wrong:0.48 × 6 > 6
0.48 is less than 1, so 0.48 × 6 is less than 6 (about half of 6).
Helpful Math Tip
Ask "about how big should this be?" before calculating. A quick whole-number estimate catches most decimal point mistakes.
Related Grade 5 Skills
Make Florida Math Practice More Fun
Help your child build math confidence with original interactive questions aligned with Florida's B.E.S.T. Mathematics Standards.
Start Practicing FreeIndependent Educational Platform. FastChomp is published by Tropical Learning LLC and is not affiliated with, sponsored by, or endorsed by the Florida Department of Education. FAST and Star assessment names are referenced for informational purposes only. FastChomp practice questions are original educational materials, not official Florida FAST assessment questions.