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The sum of two positive numbers is 40. If the GM of these two numbers is lower than their AM by 20%, then what is the difference between the two numbe
Question

The sum of two positive numbers is 40. If the GM of these two numbers is lower than their AM by 20%, then what is the difference between the two numbers?

A.

12

B.

18

C.

24

D.

28

Correct option is C

Given:

Sum of two positive numbers = 40

The GM of these two numbers is 20% lower than their AM

Concept:

AM (Arithmetic Mean) = (a + b) / 2

GM (Geometric Mean) = √(a × b)

GM = 0.8 × AM

Solution:

Let the two numbers be a and b.

a + b = 40

AM = (a + b) / 2 = 40 / 2 = 20

GM = √(a × b)

Given GM = 0.8 × AM

=> √(a × b) = 0.8 × 20

=> √(a × b) = 16

=> a × b = 162

=> a × b = 256

We have the equations:

1. a + b = 40

2. a × b = 256

Solving these two equations:

Let a and b be the roots of the quadratic equation x2- (a+b)x + ab = 0

=> x2- 40x + 256 = 0

Solving for x using the quadratic formula x = [ -b ± √(b2- 4ac) ] / 2a

=> x = [ 40 ± √(1600 - 1024) ] / 2

=> x = [ 40 ± √576 ] / 2

=> x = [ 40 ± 24 ] / 2

=> x = 32 or x = 8

So, the two numbers are 32 and 8.

Difference between the two numbers = 32 - 8 = 24

Hence, the difference between the two numbers is 24.

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