the shopkeeper increased the price of a product by 25 % so that customer finds it difficult to purchase the required amount . but somehow the customer managed to purchase only 64 % of the required amount . what is the net difference in the expenditure on that product ?
"quantity x rate = price 1 x 1 = 1 0.64 x 1.25 = 0.8 decrease in price = ( 0.2 / 1 ) × 100 = 20 % e )"
divide(multiply(subtract(multiply(const_100, const_100), multiply(add(const_100, 25), 64)), const_100), multiply(const_100, const_100))