Answer:
We have:
P1 = a x b
If a decreases by 20% and b decreases by 60%, then we have:
P2 = a x (100 - 20)/100 x b x (100 - 60)/100
= a x 80/100 x b x 40/100
= a x b x 8/25
=> P1 - P2 = ab - (8/25)ab = (17/25)ab
=> If a decreases by 20% and b decreases by 60%, product of a and b would decrease 17/25 = 0.68%
Hope this helps!
:)
