Home Favorites My Account Menu

Playwire Advertisement

finding length of a side Worksheets

This section provides worksheets where students find missing side lengths of rectangles and right triangles when given area or perimeter values. Designed for 3rd grade students, these problems include basic whole number calculations and decimal variations, helping students understand the inverse relationships in geometric formulas.

Filter By Grade

3rd Grade

Image Size

Grid Style

List Style

×

Finding Length of a Side

About these worksheets

Students practice finding a missing side length of a rectangle or right triangle when given the area or perimeter. These worksheets reinforce the relationship between side lengths, area, and perimeter through reverse calculation — dividing area by a known side or subtracting known sides from a total perimeter. Problem sets span third grade through middle school, with some including decimal values.

finding length of a side Worksheets - Missing Side (Area) E worksheet

Load up one problem at a time! Ideal for projectors, tablets and computers.

Create a set of flash cards.

Create a distance learning assignment.

Distance Learning

Create a new worksheet.

Create New Sheet

Magnify worksheet preview

Select a Worksheet >

Pin It

Missing Side (Area) E

3md8

Use the area of a rectangle to figure out a missing side length.
Divide the area by the known side to find the unknown side.
Check that the side lengths you found make the correct area when multiplied.

Add to favorites

Remove from favorites

finding length of a side Worksheets - Missing Side (Perimeter) E worksheet

Load up one problem at a time! Ideal for projectors, tablets and computers.

Create a set of flash cards.

Create a distance learning assignment.

Distance Learning

Create a new worksheet.

Create New Sheet

Magnify worksheet preview

Select a Worksheet >

Pin It

Missing Side (Perimeter) E

3md8

Use the perimeter of a rectangle to figure out one missing side length.
Add the known side lengths and subtract from the total perimeter to find what is left.
Use the fact that opposite sides of a rectangle are equal to solve for the unknown side.
Write the answer with the correct measurement units.

Add to favorites

Remove from favorites

finding length of a side Worksheets - Finding Missing Side Length of Rectangle worksheet

Load up one problem at a time! Ideal for projectors, tablets and computers.

Create a set of flash cards.

Create a distance learning assignment.

Distance Learning

Create a new worksheet.

Create New Sheet

Magnify worksheet preview

Select a Worksheet >

Pin It

Finding Missing Side Length of Rectangle

Find a missing side length of a rectangle when you know the area and one side.
Use multiplication and division to connect side lengths and area of rectangles.

Add to favorites

Remove from favorites

finding length of a side Worksheets - Finding Missing Side Length of Rectangle with Decimals worksheet

Load up one problem at a time! Ideal for projectors, tablets and computers.

Create a set of flash cards.

Create a distance learning assignment.

Distance Learning

Create a new worksheet.

Create New Sheet

Magnify worksheet preview

Select a Worksheet >

Pin It

Finding Missing Side Length of Rectangle with Decimals

Use the area of a rectangle to figure out a missing side length.
Multiply and divide with decimals to solve for an unknown side.
Keep track of units (like square units vs. units) so the answer makes sense.
Read a rectangle diagram and match each number to the correct side.

Add to favorites

Remove from favorites

finding length of a side Worksheets - Finding Missing Side Length of Right Triangle (Area) worksheet

Load up one problem at a time! Ideal for projectors, tablets and computers.

Create a set of flash cards.

Create a distance learning assignment.

Distance Learning

Create a new worksheet.

Create New Sheet

Magnify worksheet preview

Select a Worksheet >

Pin It

Finding Missing Side Length of Right Triangle (Area)

Use the area formula for a right triangle to find a missing side length.
Solve for the unknown base or height when the area and the other leg are given.

Add to favorites

Remove from favorites

Playwire Advertisement