a water tank is three - fifths full . pipe a can fill a tank in 10 minutes and pipe b can empty it in 6 minutes . if both the pipes are open , how long will it take to empty or fill the tank completely ?
"the combined rate of filling / emptying the tank = 1 / 10 - 1 / 6 = - 1 / 15 since the rate is negative , the tank will be emptied . a full tank would take 15 minutes to empty . since the tank is only three - fifths full , the time is ( 3 / 5 ) * 15 = 9 minutes the answer is d ."
divide(divide(const_4, add(const_2, const_3)), subtract(inverse(6), inverse(10)))