Question

The perimeter of a triangle is 55 cm. One its sides is 15 cm. If the other two sides are equal, find their length.

Answer 1

Given that the perimeter of triangle is 55 cm and length of one side = 15 cm
The other two sides are equal; let these be x.
Perimeter of a triangle = sum of all sides
⇒ 15 cm + x + x = 55 cm
⇒ 15 cm + 2x = 55 cm
⇒ 2x = 55 cm – 15 cm
⇒ 2x = 40 cm
$\Rightarrow x=\frac{40\mathrm{cm}}{2}=20\mathrm{cm}$
Thus, the length of other two equal sides is 20 cm each.