Question

the cost of an article is for decrease by 25% then for the decrease by 40% find the percentage change in the cost of the articles

Answer 1

Let the cost be 100
Now,
after 25% decrease, the amount become 75
and again after 40% decrease, the amount become 45
Now, the total decrease = 100-45 = 55
                   percentage = 55/100  = 11/20%

Answer 2

let be, the cost of article = 100/- = 100%
decrease % = 25 (100-25=75%)
then decrease 40%
40% of 75 = 30/-
75 - 30 = 45/-
rest cost of article = 45/-