By what percent will the product of two numbers decrease if one of them is decreased by 20% and the other is decreased by 60%?

Original product:

P1 = a x b

Decreased product:

P2 = a x (100 - 20)/100 x b x (100 - 60)

    = a x b x 80/100 x 40/100

    = a x b x 8/25

=> P1/P2 = 8/25

or

P1 is decreased by: 1 - 8/25 = 17/25 = 68%

Hope this helps!

:)