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⏰ 4th grade math · Measure, Time & Money

Area and perimeter rules

Take away the sides you know from the perimeter. What's left is shared by the two matching sides.

Worked example

The perimeter is 32 inches. How long is the side marked ? ?
?5 inches?5 inches
Answer: 11
The two sides marked 5 add up to 10. That leaves 32 − 10 = 22 for the other two sides, which match. Half of 22 is 11 inches.
11 inches5 inches11 inches5 inches

For grown-ups: Area and perimeter formulas for rectangles. Below: three problems to try with the worked answers, and a free printable sheet. Children can practise the same skill as a game, with no sign-up and no ads.

  • CCSS 4.MD.A.3
What this practises, for teachers

Practices area and perimeter formulas for rectangles (4.MD.A.3). A printable sheet with its answer key, worked answers on the page, no accounts.

▶ Practise it

For your class

🖨️ Printable sheet and key

Try three

  1. The perimeter is 18 feet. How long is the side marked ? ?
    ?7 feet?7 feet
    Show the answer and how
    Answer: 2
    The two sides marked 7 add up to 14. That leaves 18 − 14 = 4 for the other two sides, which match. Half of 4 is 2 feet.
    2 feet7 feet2 feet7 feet
  2. The perimeter is 44 feet. How long is the side marked ? ?
    ?9 feet?9 feet
    Show the answer and how
    Answer: 13
    The two sides marked 9 add up to 18. That leaves 44 − 18 = 26 for the other two sides, which match. Half of 26 is 13 feet.
    13 feet9 feet13 feet9 feet
  3. The perimeter is 16 inches. How long is the side marked ? ?
    ?6 inches?6 inches
    Show the answer and how
    Answer: 2
    The two sides marked 6 add up to 12. That leaves 16 − 12 = 4 for the other two sides, which match. Half of 4 is 2 inches.
    2 inches6 inches2 inches6 inches

Before and after

Learn first: Change inches to feet (4th)

Comes next: Measure angles (4th)

Name: ____________________Date: ____________Score: ____ / 12

Area and perimeter rules (4th grade)

  1. The perimeter is 38 feet. How long is the side marked ? ?
    ?9 feet?9 feet
  2. The perimeter is 42 feet. How long is the side marked ? ?
    ?9 feet?9 feet
  3. The perimeter is 18 feet. How long is the side marked ? ?
    ?3 feet?3 feet
  4. The perimeter is 26 centimeters. How long is the side marked ? ?
    ?4 centimeters?4 centimeters
  5. The perimeter is 28 meters. How long is the side marked ? ?
    ?2 meters?2 meters
  6. The perimeter is 28 inches. How long is the side marked ? ?
    ?2 inches?2 inches
  7. The perimeter is 26 meters. How long is the side marked ? ?
    ?2 meters?2 meters
  8. The perimeter is 40 centimeters. How long is the side marked ? ?
    ?6 centimeters?6 centimeters
  9. The perimeter is 18 centimeters. How long is the side marked ? ?
    ?5 centimeters?5 centimeters
  10. The perimeter is 44 feet. How long is the side marked ? ?
    ?7 feet?7 feet
  11. The perimeter is 18 centimeters. How long is the side marked ? ?
    ?6 centimeters?6 centimeters
  12. The perimeter is 18 feet. How long is the side marked ? ?
    ?5 feet?5 feet

Answer key

  1. 10
  2. 12
  3. 6
  4. 9
  5. 12
  6. 12
  7. 11
  8. 14
  9. 4
  10. 15
  11. 3
  12. 4

More 4th grade skills: all 4th grade math skills, or every grade at math skills.