GeometryMissing edge
Name: Date:
The volume of each box is shown. Find the missing edge, in centimeters.
1 cm
2 cm
3 cm
4 cm
5 cm
6 cm
Missing edge from the volume worksheets
If a box holds 120 cm³ and two of its edges are 4 and 5, the third has to be 6 — because 4 × 5 × 6 is 120. These free printable worksheets run the volume formula backward: the box shows its volume and two edges, and you find the one marked x.
Kid stuck on one? You don’t just get the sheet.
Missing edge from the volume
The answer key prints on a separate page.
What's on this sheet
It is the volume sheet's inverse, the way finding a missing side is the area sheet's. Volume is length × width × height, so if you know the volume and two edges, the third is the volume divided by the product of the other two. Multiplying the two you have first — into a single number to divide by — is the step that keeps it one division rather than two.
Why this sheet works
Every box is built from three whole edges, so the volume divides evenly and the missing edge is always a whole number — never 6.4. The figure is the same oblique box the volume sheets draw, in true proportion, so a child can see which edge is missing rather than hunt for it in a sentence.
How this one works
One question from this sheet, worked through a step at a time.
Missing edge of a box, volume 90
6 × 3 × x=90
6 × 3=18
90 ÷ 18=5
- The volume of a box is its three edges multiplied: length × width × height. You have the height (6), the depth (3), and the volume (90).
- Multiply the two edges you know first: 6 × 3 = 18.
- Then the missing edge is the volume divided by that: 90 ÷ 18 = 5.