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Mathematics

The altitude of a right triangle is 17 cm less than its base. If the hypotenuse is 25 cm, then the perimeter of the triangle is :

  1. 48 cm

  2. 56 cm

  3. 54 cm

  4. 64 cm

Quadratic Equations

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Answer

Let the base and height of right triangle be x cm and (x - 17) cm respectively.

By pythagoras theorem,

⇒ Base2 + Height2 = Hypotenuse2

⇒ x2 + (x - 17) 2 = (25)2

⇒ x2 + x2 + (17)2 - 2 × x × 17 = 625

⇒ x2 + x2 + 289 - 34x = 625

⇒ 2x2 - 34x + 289 - 625 = 0

⇒ 2x2 - 34x - 336 = 0

⇒ 2(x2 - 17x - 168) = 0

⇒ x2 - 17x - 168 = 0

⇒ x2 - 24x + 7x - 168 = 0

⇒ x(x - 24) + 7(x - 24) = 0

⇒ (x + 7)(x - 24) = 0

⇒ (x + 7) = 0 or (x - 24) = 0     [Using zero -product rule]

⇒ x = -7 or x = 24.

Since, the length of triangle cannot be negative, x ≠ -7.

x - 17 = 24 - 17 = 7.

The perimeter of right triangle is = 7 + 24 + 25 = 56 cm.

Hence, option 2 is the correct option.

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