Solved Questions of Perimeter of a Triangle
1. The perimeter of a triangle is 48 cm. If one side has a length of 17 cm and another side has a length of 18 cm, what is the length of the third side?
a) 13 cm
b) 18 cm
c) 21 cm
d) 30 cm
Answer: a) 13 cm
Explanation: We can use the formula P = a + b + c and put the given values to get 48 cm = 17 cm + 18 cm + c.
Solving for c, we get c = 13 cm
So, the length of the third side is 13 cm.
2. A triangle has sides with lengths of 6 cm, 8 cm and 10 cm. What is its perimeter?
a) 20 cm
b) 24 cm
c) 28 cm
d) 32 cm
Answer: b) 24 cm
Explanation: Using the formula P = a + b + c,
we get P = 6 cm + 8 cm + 10 cm = 24 cm.
3. If an equilateral triangle has a perimeter of 21 cm, what is the length of each of its sides?
a) 3 cm
b) 7 cm
c) 21 cm
d) 63 cm
Answer: b) 7 cm
Explanation: Using the formula P = 3a, where a is the side of equilateral triangle on putting the value of perimeter in the formula
P = 3a
21 = 3a
a = 21/3
a = 7 cm
4. An isosceles triangle has a perimeter of 24 cm. If one side is 7 cm long, what are the lengths of the other two equal sides?
a) 8.5 cm each
b) 8 cm each
c) 8 cm and 9 cm
d) 9 cm each
Answer: a) 8.5 cm each
Explanation: Since the perimeter is 24 cm and one side is 7 cm, the sum of the other two sides must be: 24 cm - 7 cm = 17 cm.
Since the triangle is isosceles, the other two sides must be equal in length. Thus, each of the other two sides has a length: (17 cm / 2) = 8.5 cm.
Therefore, the lengths of the other two sides are 8.5 cm each.
5. A triangle has sides with lengths of 5 cm, 6 cm and 8 cm. What is its perimeter?
a) 10 cm
b) 14 cm
c) 18 cm
d) 19 cm
Answer: d) 19 cm
Explanation: Using the formula P = a + b + c,
we get P = 5 cm + 6 cm + 8 cm = 19 cm
Practice Questions of Perimeter of a Triangle
1. What is the perimeter of a triangle with sides of 5 cm, 7 cm and 9 cm?
a) 21 cm
b) 22 cm
c) 23 cm
d) 24 cm
Answer: a) 21 cm
2. The perimeter of a right-angled triangle is 40 cm. If the length of the hypotenuse is 25 cm, what is the sum of length of the other two sides?
a) 15 cm
b) 20 cm
c) 25 cm
d) 30 cm
Answer: a) 15 cm
3. What is the perimeter of an equilateral triangle with a side length of 5 cm?
a) 10 cm
b) 15 cm
c) 20 cm
d) 25 cm
Answer: b) 15 cm
4. An equilateral triangle has a side length of 8 cm. What is its perimeter?
a) 16 cm
b) 24 cm
c) 32 cm
d) 48 cm
Answer: b) 24 cm
5. The perimeter of an isosceles triangle is 21 m. If the length of an equal side is 6 m, what is the length of the base?
a) 6 m
b) 9 m
c) 12 m
d) 18 m
Answer: b) 9 m
6. The perimeter of an isosceles triangle is 30 cm and equal side has a length of 9 cm. What is the length of the other side?
a) 6 cm
b) 9 cm
c) 12 cm
d) 18 cm
Answer: c) 12 cm
7. An equilateral triangle has a side length of 10 cm. What is its perimeter?
a) 16 cm
b) 24 cm
c) 30 cm
d) 48 cm
Answer: c) 30 cm
8. An equilateral triangle has a side length of 20 cm. What is its perimeter?
a) 16 cm
b) 24 cm
c) 32 cm
d) 60 cm
Answer: d) 60 cm
9. A triangle has sides with lengths of 10 cm, 12 cm and 18 cm. What is its perimeter?
a) 20 cm
b) 24 cm
c) 28 cm
d) 40 cm
Answer: d) 40 cm
10. A triangle has sides with lengths of 12 cm, 14 cm and 20 cm. What is its perimeter?
a) 20 cm
b) 24 cm
c) 28 cm
d) 46 cm
Answer: d) 46 cm
