In Grade 5, students solve real-world volume problems with rectangular prisms, including problems where one edge length is missing.
When the volume and two edges are known, divide the volume by the area of the base (the product of the two known edges) to find the missing edge.
Official benchmarkSolve real-world problems involving the volume of right rectangular prisms, including problems with an unknown edge length, with whole-number edge lengths using a visual model or a formula.
On the FAST test: part of the Grade 5 reporting category Geometric Reasoning, Measurement, and Data Analysis and Probability, which is about 23–29% of the test.
Worked Examples
Worked Example 1
Finding Volume
A box is 12 in long, 5 in wide, and 4 in tall. What is its volume?
1V = 12 × 5 × 4.
212 × 5 = 60; 60 × 4 = 240.
Answer: 240 cubic inches
Worked Example 2
Missing Edge
A box has a volume of 180 cubic cm. It is 6 cm long and 5 cm wide. How tall is it?Volume = 180 cubic cm
1Base area: 6 × 5 = 30 sq cm.
2Height: 180 ÷ 30 = 6 cm.
3Check: 6 × 5 × 6 = 180.
Answer: 6 cm
Common Mistakes to Watch For
Dividing by only one edge
Wrong:180 ÷ 6 = 30 cm tall
Divide by the whole base area: 180 ÷ (6 × 5) = 180 ÷ 30 = 6 cm.
Forgetting to add parts of a combined shape
Wrong:Two boxes: only the bigger one is counted
Find each box's volume separately, then add them together.
Helpful Math Tip
Check a missing-edge answer by multiplying all three edges. You should get the volume from the problem.
Independent 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.
