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The sum of two positive numbers x and y is 50 and the difference of their squares is 720. Find the numbers. - Mathematics

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Question

The sum of two positive numbers x and y (x > y) is 50 and the difference of their squares is 720. Find the numbers.

Sum

Solution

Two numbers are x and y such that x > y.

x + y = 50       ...(i)

x2 - y2 = 720

⇒ (x + y)(x - y) = 720

⇒ 50(x - y) = 720   ...[Using equation (i)]

⇒ x - y = `720/50`

⇒ x - y = 14.4                     ….(ii)

Adding (i) and (ii), we get

   x + y = 50
+ x - y = 14.4
2x = 64.4

x = `(64.4)/2`

⇒ x = 32.2

Substituting the value of x in (i), we have

x + y = 50

32.2+ y = 50

⇒ y = 50 - 32.2

⇒ y = 17.8

Thus, the two numbers are 17.8 and 32.2 respectively.

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Chapter 6: Simultaneous (Linear) Equations (Including Problems) - Exercise 6 (E) [Page 90]

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Selina Concise Mathematics [English] Class 9 ICSE
Chapter 6 Simultaneous (Linear) Equations (Including Problems)
Exercise 6 (E) | Q 4 | Page 90
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