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The Difference of Squares of Two Numbers is 180. the Square of the Smaller Number is 8 Times the Larger Number. Find the Two Numbers - CBSE Class 10 - Mathematics

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Question

The difference of squares of two numbers is 180. The square of the smaller number is 8 times the larger number. Find the two numbers

Solution

Let the larger and smaller number be x and y respectively.

According to the question,

x2 - y2 = 180 and y2 = 8x

⇒ x2 - 8x = 180

⇒ x2 - 8x - 180 = 0

⇒ x2- 18x + 10x - 180 = 0

⇒ x(x - 18) +10(x - 18) = 0

⇒ (x - 18)(x + 10) = 0

⇒ x = 18, -10

However, the larger number cannot be negative as 8 times of the larger number will be negative and hence, the square of the smaller number will be negative which is not possible.

Therefore, the larger number will be 18 only.

x = 18

∴ y2 = 8x = 8 × 18 = 144

⇒ y = `±sqrt144 = ±12`

∴ Smaller number = ±12

Therefore, the numbers are 18 and 12 or 18 and - 12.

  Is there an error in this question or solution?

APPEARS IN

 NCERT Solution for Mathematics Textbook for Class 10 (2019 to Current)
Chapter 4: Quadratic Equations
Ex. 4.30 | Q: 7 | Page no. 88
Solution The Difference of Squares of Two Numbers is 180. the Square of the Smaller Number is 8 Times the Larger Number. Find the Two Numbers Concept: Solutions of Quadratic Equations by Completing the Square.
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