Worked Example 1
Decimal Unknown
Solve 2.4 × n = 8.4.
- 1Divide: n = 8.4 ÷ 2.4
- 28.4 ÷ 2.4 = 3.5
Answer: n = 3.5
Florida Grade 6 Math · Algebraic Reasoning
MA.6.AR.2.4: Finding Unknown Decimals and Fractions
What this Grade 6 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.6.AR.2.4?
Students find the unknown positive decimal or fraction in an equation with three numbers and any of the four operations. The unknown can be in any position.
Algebraic reasoning, drawings, and mental math all help. For example, in 98 = x − 18, x must be 18 more than 98, so x = 108.
Official benchmarkDetermine the unknown decimal or fraction in an equation involving any of the four operations, relating three numbers, with the unknown in any position.
On the FAST test: part of the Grade 6 reporting category Algebraic Reasoning, which is about 25–36% of the test.
Worked Examples
Worked Example 2
Fraction Unknown
Solve 34 ÷ y = 18.
- 134 split into groups of size y gives 18, so y = 34 ÷ 18.
- 234 ÷ 18 = 34 × 8 = 6
Answer: y = 6
Common Mistakes to Watch For
Using the wrong inverse operation
Wrong:x − 1.6 = 4.2, so x = 4.2 − 1.6 = 2.6
Undo subtracting by adding: x = 4.2 + 1.6 = 5.8.
Dividing in the wrong order
Wrong:2.4 × n = 8.4, so n = 2.4 ÷ 8.4
The product (8.4) is divided by the known factor: n = 8.4 ÷ 2.4 = 3.5.
Helpful Math Tip
Estimate before solving: in 2.4 × n = 8.4, n must be between 3 and 4 because 2.4 × 3 = 7.2 and 2.4 × 4 = 9.6.
Related Grade 6 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.