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The perimeter of a right triangle is 60 cm and its hypotenuse is 25 cm. Find the area of the triangle.

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Let △ABC be the right triangle.

The perimeter of a right triangle is 60 cm and its hypotenuse is 25 cm. Find the area of the triangle. ARC Properties of Circle, R.S. Aggarwal Mathematics Solutions ICSE Class 9.

We know that,

Perimeter of a right-angled triangle = 60 cm

Hypotenuse = 25 cm

So, the sum of other two sides of triangle = 60 – 25 = 35 cm

Let, base (BC) = x cm

So, AB = (35 - x) cm

Using the Pythagoras theorem,

⇒ AC2 = AB2 + BC2

⇒ 252 = (35 - x)2 + x2

⇒ 625 = 1225 + x2 - 70x + x2

⇒ 2x2 - 70x + 600 = 0

Dividing by 2 on both sides,

⇒ x2 - 35x + 300 = 0

⇒ x2 - 15x - 20x + 300 = 0

⇒ x(x – 15) - 20(x - 15) = 0

⇒ (x - 15)(x - 20) = 0

⇒ x - 15 = 0 or x - 20 = 0

⇒ x = 15 or x = 20.

If x = 15, then 35 - x = 35 - 15 = 20 cm.

If x = 20, then 35 - x = 35 - 20 = 15 cm.

So, length of other two sides apart from hypotenuse are 15 cm and 20 cm.

Area of triangle = 12\dfrac{1}{2} × base × height

Substituting the values we get,

A = 12\dfrac{1}{2} × 15 × 20 = 150 cm2.

Hence, area of triangle = 150 cm2.

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