if it takes a tub 4 minutes to drain 5 / 7 of its content , how much more time will it take for the tub to be empty ?
"if 5 / 7 of tub ' s content is drained 2 / 7 th of tub still needs to be drained . if it takes 4 minutes to drain 5 / 7 th of tub it takes 4 * ( 7 / 5 ) minutes to drain the entire tub and 4 * ( 7 / 5 ) * ( 2 / 7 ) min to drain 2 / 7 th of the tub which is 8 / 5 minutes or 1 3 / 5 minutes or 1 minute 36 seconds so answer is c"
add(subtract(const_1, divide(5, 7)), divide(5, 7))