If the sum and the difference of two numbers are 20 and 8 respectively, then the difference of their square is Choose the correct answer.
A) 12
B) 28
C) 160
D) 180
E) None
Solution   Let the numbers be x and y.   Then, x + y = 20 and x - y = 8.   Therefore,x2 - y2 = (x + y)(x - y)   ‹=› 20 x 8   ‹=› 160.   Answer 160
<result>C</result>
If the sum and the difference of two numbers are 20 and 8 respectively, then the difference of their square is