a cistern can be filled by a tap in 4 hours while it can be emptied by another tap in 11 hours . if both the taps are opened simultaneously , then after how much time will the cistern get filled ?
"net part filled in 1 hour = ( 1 / 4 - 1 / 11 ) = 7 / 44 the cistern will be filled in 44 / 7 hrs i . e . , 6.28 hrs . answer : d"
divide(const_1, subtract(divide(const_1, 4), divide(const_1, 11)))