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The sum of two numbers is 10 and the difference in their squares is 60. What are the two numbers?
Question

The sum of two numbers is 10 and the difference in their squares is 60. What are the two numbers?

A.

5 and 5

B.

8 and 2

C.

7 and 3

D.

6 and 4

Correct option is B

Given:

Sum of two numbers = 10

Difference of their squares = 60

Concept Used:

Algebraic equations and solving them.

a² - b² = (a + b)(a - b)

Solution:

Let the two numbers be x and y.

x + y = 10 (Equation 1)

x² - y² = 60 (Equation 2)

x² - y² = (x + y)(x - y)

Substitute the given value: (x + y)(x - y) = 60

Substitute the value of (x + y) from Equation 1:

10(x - y) = 60

x - y = 6 (Equation 3)

Solve Equations 1 and 3 simultaneously:

x + y = 10

x - y = 6

Add the two equations: 2x = 16

x = 8

Substitute the value of x in Equation 1:

8 + y = 10

y = 2

Therefore, the two numbers are 8 and 2.

Alternate Solution:

From x+y=10, we can say x=10-y.

Substitute that into x²-y²=60.

(10-y)²-y²=60

100-20y+y²-y²=60

100-20y=60

40=20y

y=2

Substitute y=2 into x+y=10.

x+2=10

x=8.

The numbers are 8 and 2.

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