if a man lost 10 % by selling oranges at the rate of 10 a rupee at how many a rupee must he sell them to gain 50 % ?
"90 % - - - - 10 150 % - - - - ? 90 / 150 * 10 = 6 answer : a"
divide(multiply(subtract(const_100, 10), 10), add(const_100, 50))