Question

The difference and product of two numbers is 10 and 20 respectively. Find the difference of their squares.

• A. 140
• B. 120
• C. 80
• D. 100

Answer 1

The correct option is A

140

Let the two numbers be x and y.

Given: x-y = 10 and xy = 20

We know the identity $(x-y{)}^2$ = $x^2$ + $y^2$ - 2xy

Which gives ${10}^2$ = $x^2$ + $y^2$ - 40

Hence $x^2$ + $y^2$ = 100 + 40 = 140