Shape and space · Ages 8–9

Kinds of triangle worksheet

Part of: Parallel lines, quadrilaterals and triangles

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Shape and space · Ages 8–9

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Write each answer in the space. For word problems, show your working and write a sentence answer.

1.One side of an equilateral triangle is 2 cm. How long are its three sides altogether?
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2.An isosceles triangle has two legs of 16 cm and a base of 15 cm. How long are its three sides altogether?
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3.One side of an equilateral triangle is 30 cm. How long are its three sides altogether?
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4.An isosceles triangle has two legs of 11 cm and a base of 7 cm. How long are its three sides altogether?
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5.An isosceles triangle has two legs of 7 cm and a base of 5 cm. How long are its three sides altogether?
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6.One side of an equilateral triangle is 25 cm. How long are its three sides altogether?
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7.One side of an equilateral triangle is 27 cm. How long are its three sides altogether?
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8.An isosceles triangle has two legs of 10 cm and a base of 9 cm. How long are its three sides altogether?
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9.Lines are drawn from the top corner of the big triangle down to its base. How many triangles are there in the picture altogether?
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13.Ka-yee bends a 81 cm wire into an equilateral triangle, using all of it. How long is each side?
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14.An equilateral triangle and a square both have sides of 13 cm. How long are all the sides of both shapes altogether?
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15.An isosceles flower bed has sides adding up to 12 m, with a base of 2 m. How long is each leg?
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16.An equilateral triangle and a square both have sides of 11 cm. How long are all the sides of both shapes altogether?
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17.Tsz-ching bends a 18 cm wire into an equilateral triangle, using all of it. How long is each side?
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18.An isosceles flower bed has sides adding up to 45 m, with a base of 11 m. How long is each leg?
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Show the answers and working

Kinds of triangle worksheet: Answers and working

1. 6 cm
An equilateral triangle's three sides are all the same: 2 cm each. How many such sides are there?
All three sides are equal: 2 × 3 = 6.
2. 47 cm
The three sides are two 16 cm legs and a 15 cm base. Add them up.
The two legs are equal: 16 + 16 + 15 = 47.
3. 90 cm
An equilateral triangle's three sides are all the same: 30 cm each. How many such sides are there?
All three sides are equal: 30 × 3 = 90.
4. 29 cm
The three sides are two 11 cm legs and a 7 cm base. Add them up.
The two legs are equal: 11 + 11 + 7 = 29.
5. 19 cm
The three sides are two 7 cm legs and a 5 cm base. Add them up.
The two legs are equal: 7 + 7 + 5 = 19.
6. 75 cm
An equilateral triangle's three sides are all the same: 25 cm each. How many such sides are there?
All three sides are equal: 25 × 3 = 75.
7. 81 cm
An equilateral triangle's three sides are all the same: 27 cm each. How many such sides are there?
All three sides are equal: 27 × 3 = 81.
8. 29 cm
The three sides are two 10 cm legs and a 9 cm base. Add them up.
The two legs are equal: 10 + 10 + 9 = 29.
9. 6 triangles
Count the smallest triangles first, then those made of two next to each other, and so on. Don't forget the biggest one.
There are 3 smallest triangles; then count those made of two, three, … side by side, the biggest one too: 6 in all.

10. C. Equilateral
Look at the side lengths 4, 4 and 4 cm first. How many are equal?
The sides are 4, 4 and 4 cm: count how many are equal.
11. False
Look at the triangle's three corners for a right-angle mark (a small square).
Only a triangle with a right-angle mark (the small square) is right-angled.
12. A. Right-angled
Find the right-angle mark first, then check whether the two sides beside it are the same length.
It has a right angle; the sides beside it are 4 and 6 cm — equal means isosceles right-angled.

Marking: 2 for the working, 1 for the answer, 1 for the sentence.

13. 27 cm
An equilateral triangle's three sides are equal. Into how many equal parts is the 81 cm shared?
Three equal sides: 81 ÷ 3 = 27.
14. 91 cm
How many sides does the triangle have, and the square? Each is 13 cm.
3 sides and 4 sides make 7: 13 × 7 = 91.
15. 5 m
Take the 2 m base from 12 m first to find how long the two legs are together.
The two legs make 12 − 2; each is half: 5 m.
16. 77 cm
How many sides does the triangle have, and the square? Each is 11 cm.
3 sides and 4 sides make 7: 11 × 7 = 77.
17. 6 cm
An equilateral triangle's three sides are equal. Into how many equal parts is the 18 cm shared?
Three equal sides: 18 ÷ 3 = 6.
18. 17 m
Take the 11 m base from 45 m first to find how long the two legs are together.
The two legs make 45 − 11; each is half: 17 m.

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