pipe a fills a swimming pool in 4 hours . pipe b empties the pool in 6 hours . if pipe a was opened at 6 : 00 am and pipe b at 7 : 00 am , at what time will the pool be full ?
"pipe a fills the pool in 4 hrs . 1 hour ' s work : 1 / 4 pipe b empties the pool in 6 hrs . 1 hour ' s work : 1 / 6 together if they work , 1 hour ' s work = 1 / 4 - 1 / 6 = 1 / 12 given : pipe a started at 6 : 00 a . m and pipe b at 7 : 00 a . m pool filled after 1 hour by pipe a : 1 / 4 or 3 / 12 after 7 : 00 a . m pool filled after 1 hour with both the pipes on : 1 / 12 pool filled after 9 hours with both pipes on : 9 / 12 pool filled in 1 hour + pool filled in 9 hours = 3 / 12 + 9 / 12 = 1 therefore , it takes 10 hrs to fill the pool as pipe a started at 6 : 00 a . m , pool is full at 16 : 00 hrs answer : d"
multiply(divide(const_3, 4), divide(const_1, subtract(divide(const_1, 4), divide(const_1, 6))))