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The sum of the squares of two positive integers is 208. If the square of the large number is 18 times the smaller. Find the numbers. - Mathematics

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Question

The sum of the squares of two positive integers is 208. If the square of the large number is 18 times the smaller. Find the numbers.

Sum

Solution

Let the two numbers be x and y, y being the bigger number.

From the given information,

x+ y= 208  ...(i)

y2 = 18x   ...(ii)

From (i), we get y2 = 208 – x2

Putting this in (ii), we get,

208 – x= 18x

⇒ x2 + 18x – 208 = 0

⇒ x2 + 26x – 8x – 208 = 0

⇒ x(x + 26) – 8(x + 26) = 0

⇒ (x – 8)(x + 26) = 0

⇒ x can't be a negative number, hence x = 8

⇒ Putting x = 8 in (ii), we get y2 = 18 × 8 = 144

⇒ y = 12, since y is a positive integer

Hence, the two numbers are 8 and 12.

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Problems Based on Numbers
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Chapter 6: Solving (simple) Problems (Based on Quadratic Equations) - Exercise 6 (A) [Page 70]

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Selina Mathematics [English] Class 10 ICSE
Chapter 6 Solving (simple) Problems (Based on Quadratic Equations)
Exercise 6 (A) | Q 7 | Page 70
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