Question

Mohan decreased 15% his expense and later on decreased it by 5% more . How many % did his expense decrease?

Answer 1

assume that his expense is rs.1000
first decrease in expense = 15/100 *1000 which is 150 subtracting it from the original expense we get 850.
5% decrease on it (850) = 5/100*850 which gives 42.5 again subtracting it from the expense (850) we get 807.5
so the total decrease in expense = 807.5/1000*100
and the answer is 80.75%

Answer 2

the Shortcut Formula is as follows :          Net  Decrease = -15 - 5 + (15*5)/100                                 => Net Decrease = -20 + 75 /100 = (-2000 +75) /100 = -1925 /100   = 19.25                  Hence Net Decrease = 19.25%