The perimeter of the triangle is 19units. The length of one side is missing.

To find the missing side length, write an addition number sentence for the perimeter of the triangle. The perimeter of a triangle equals the sum of all of its side lengths.

7+7+?=perimeter

The perimeter is 19units.

7+7+?=19

Add the lengths of the sides you know.

14+?=19

Find the side length that makes the addition number sentence true.

14+5=19

The missing side length is 5units.

The perimeter of the shape is 17units. The length of one side is missing.

To find the missing side length, write an addition number sentence for the perimeter of the shape. The perimeter of a shape equals the sum of all of its side lengths.

3+4+?+4=perimeter

The perimeter is 17units.

3+4+?+4=17

Add the lengths of the sides you know.

11+?=17

Find the side length that makes the addition number sentence true.

11+6=17

The missing side length is 6units.

The perimeter of the shape is 20units. The length of one side is missing.

To find the missing side length, write an addition number sentence for the perimeter of the shape. The perimeter of a shape equals the sum of all of its side lengths.

?+5+7+5=perimeter

The perimeter is 20units.

?+5+7+5=20

Add the lengths of the sides you know.

17+?=20

Find the side length that makes the addition number sentence true.

17+3=20

The missing side length is 3units.