Perimeter Missing Side

Answer Key - Grade 3 Math Worksheet - Building Confidence

Write the answer on the line, or circle the answer.

1. 1.

   The perimeter is 25 cm. Three sides are 5 cm, 9 cm and 5 cm. How long is the missing side, in cm?

   6
2. 2.

   The perimeter is 13 m. Three sides are 3 m, 2 m and 2 m. Which expression finds the missing side?

   • 3 + 2 + 2
   • 13 - (3 + 2 + 2)
   • 13 - 3
3. 3.

   The perimeter is 21 inches. Three sides are 4 inches, 8 inches and 4 inches. How long is the missing side, in inches?

   5
4. 4.

   Dad needs 27 m of fence to go all the way around the garden bed. Three sides are 7 m, 5 m and 5 m. How long is the fourth side, in m?

   10
5. 5.

   A rectangle has a perimeter of 18 cm. Each long side is 6 cm. How long is each short side, in cm?

   3
6. 6.

   The perimeter is 29 m. Three sides are 8 m, 5 m and 5 m. Which expression finds the missing side?

   • 29 - 8
   • 29 - (8 + 5 + 5)
   • 8 + 5 + 5
7. 7.

   The perimeter is 14 inches. Three sides are 2 inches, 6 inches and 2 inches. How long is the missing side, in inches?

   4
8. 8.

   Mia uses 13 cm of ribbon to go all the way around a paper shape she cut out. Three sides are 3 cm, 2 cm and 2 cm. How long is the fourth side, in cm?

   6
9. 9.

   The perimeter is 25 cm. Three sides are 5 cm, 8 cm and 5 cm. How long is the missing side, in cm?

   7
10. 10.

    A rectangle has a perimeter of 12 m. Each long side is 4 m. How long is each short side, in m?

    2