if a+b=15 and a-b= 1, then ab=?

if a+b=15 and a-b= 1, then ab=?

A 20

B 30

C 56

D 72

Solution

Correct Answer: Option C

here, a+b=15-----(i) a-b =1------(ii) i+ii→ 2a=16 or, a=8 i-ii →2b=14 or, b=7 so, ab= 7 x 8 =56