Divide 20 into two parts such that the sum of their squares is 272. The larger of two parts is square of the other. Assuming the smaller part to be ‘x’, form an…

ICSE Class 10 Mathematics PYQ · 2025 Improvement · Section B

8(iii)Written · 2025 · Section B · 2025 Improvement

Divide 20 into two parts such that the sum of their squares is 272. The larger of two parts is square of the other. Assuming the smaller part to be ‘x’, form an equation and solve it to find the two parts.

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Let two parts be x and (20 - x).

Given,

Sum of squares = 272

⇒ x2 + (20 - x)2 = 272

⇒ x2 + (400 - 2 × 20 × x + x2) = 272

⇒ x2 + (400 - 40x + x2) = 272

⇒ 2x2 - 40x + 400 = 272

⇒ 2x2 - 40x + 400 - 272 = 0

⇒ 2x2 - 40x + 128 = 0

⇒ 2(x2 - 20x + 64) = 0

⇒ x2 - 20x + 64 = 0

⇒ x2 - 16x - 4x + 64 = 0

⇒ x(x - 16) - 4(x - 16) = 0

⇒ (x - 4) = 0 or (x - 16) = 0     [Using zero product rule]

⇒ x = 4 or x = 16.

Hence, the two parts are 4 and 16.

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