Let’s solve each problem one by one.
We are told:
> “What is the length of the unknown side? (It gives the perimeter of the following shape.)”
That means — for each shape, we’re given the total perimeter and some side lengths. We need to find the missing side(s) so that when you add all sides together, you get the given perimeter.
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Shape 1 (top left):
Given:
- Perimeter = 40 cm
- Known sides: 5 cm, 8 cm, 9 cm, 6 cm, 7 cm
- Unknown side = ?
Add known sides:
5 + 8 = 13
13 + 9 = 22
22 + 6 = 28
28 + 7 = 35
So, unknown side = 40 - 35 =
5 cm
✔ Check: 5+8+9+6+7+5 = 40 → Correct.
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Shape 2 (top middle):
Given:
- Perimeter = 36 cm
- Known sides: 5 cm, 6 cm, 5 cm, 7 cm, 5 cm
- Unknown side = ?
Add known sides:
5 + 6 = 11
11 + 5 = 16
16 + 7 = 23
23 + 5 = 28
Unknown side = 36 - 28 =
8 cm
✔ Check: 5+6+5+7+5+8 = 36 → Correct.
---
Shape 3 (top right):
Given:
- Perimeter = 22 cm
- Known sides: 3 cm, 3 cm, 4 cm, 3 cm, 3 cm
- Unknown side = ?
Add known sides:
3+3=6; 6+4=10; 10+3=13; 13+3=16
Unknown side = 22 - 16 =
6 cm
✔ Check: 3+3+4+3+3+6 = 22 → Correct.
---
Shape 4 (middle left):
Given:
- Perimeter = 40 cm
- Known sides: 5 cm, 8 cm, 5 cm, 5 cm, 5 cm
- Unknown side = ?
Add known sides:
5+8=13; 13+5=18; 18+5=23; 23+5=28
Unknown side = 40 - 28 =
12 cm
✔ Check: 5+8+5+5+5+12 = 40 → Correct.
---
Shape 5 (middle middle):
Given:
- Perimeter = 36 cm
- Known sides: 5 cm, 5 cm, 5 cm, 5 cm, 5 cm
- Unknown side = ?
Add known sides:
5×5 = 25
Unknown side = 36 - 25 =
11 cm
✔ Check: 5+5+5+5+5+11 = 36 → Correct.
---
Shape 6 (middle right):
Given:
- Perimeter = 40 cm
- Known sides: 3 cm, 3 cm, 3 cm, 3 cm, 3 cm
- Unknown side = ?
Add known sides:
3×5 = 15
Unknown side = 40 - 15 =
25 cm
✔ Check: 3+3+3+3+3+25 = 40 → Correct.
---
Shape 7 (bottom left):
Given:
- Perimeter = 28 cm
- Known sides: 5 cm, 3 cm, 3 cm, 3 cm, 3 cm
- Unknown side = ?
Add known sides:
5+3=8; 8+3=11; 11+3=14; 14+3=17
Unknown side = 28 - 17 =
11 cm
✔ Check: 5+3+3+3+3+11 = 28 → Correct.
---
Shape 8 (bottom middle):
Given:
- Perimeter = 24 cm
- Known sides: 3 cm, 3 cm, 3 cm, 3 cm, 3 cm
- Unknown side = ?
Add known sides:
3×5 = 15
Unknown side = 24 - 15 =
9 cm
✔ Check: 3+3+3+3+3+9 = 24 → Correct.
---
Shape 9 (bottom right):
Given:
- Perimeter = 32 cm
- Known sides: 5 cm, 5 cm, 5 cm, 5 cm, 5 cm
- Unknown side = ?
Add known sides:
5×5 = 25
Unknown side = 32 - 25 =
7 cm
✔ Check: 5+5+5+5+5+7 = 32 → Correct.
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Final Answer:
5 cm, 8 cm, 6 cm, 12 cm, 11 cm, 25 cm, 11 cm, 9 cm, 7 cm
Parent Tip: Review the logic above to help your child master the concept of composite figure area worksheet.
