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hi can you explain exactly how you get 12? isn t it: 1/20+ 1/30 = 30+20/60 = 50/60 ?jayhawk2001 wrote:You have to use the rate formula here
1/t = 1/t1 + 1/t2 = 1/30 + 1/20 = 1/12
So, 12 minutes
Put another way, in each minute the pipes can fill 1/30 and 1/20 of the
pool respectively. So, combined the hoses can fill (1/30 + 1/20) of the
pool per minute. The reciprocal of this value will give you the time
required to fill the pool when both hoses are used.
@caterina!cat er ina wrote:hi can you explain exactly how you get 12? isn t it: 1/20+ 1/30 = 30+20/60 = 50/60 ?jayhawk2001 wrote:You have to use the rate formula here
1/t = 1/t1 + 1/t2 = 1/30 + 1/20 = 1/12
So, 12 minutes
Put another way, in each minute the pipes can fill 1/30 and 1/20 of the
pool respectively. So, combined the hoses can fill (1/30 + 1/20) of the
pool per minute. The reciprocal of this value will give you the time
required to fill the pool when both hoses are used.
OOOPs :roll: thank you!!gmatmachoman wrote:@caterina!cat er ina wrote:hi can you explain exactly how you get 12? isn t it: 1/20+ 1/30 = 30+20/60 = 50/60 ?jayhawk2001 wrote:You have to use the rate formula here
1/t = 1/t1 + 1/t2 = 1/30 + 1/20 = 1/12
So, 12 minutes
Put another way, in each minute the pipes can fill 1/30 and 1/20 of the
pool respectively. So, combined the hoses can fill (1/30 + 1/20) of the
pool per minute. The reciprocal of this value will give you the time
required to fill the pool when both hoses are used.
U missed the whole point there!!!
It is supposed to be 50 /600 instead of 50/60...( seems u missed a ZERO)!!
It happens....!!!
Let pool = 60 liters.cveluswamy wrote:At a constant Rate of flow, it takes 20 minutes to fill a swimming pool if a large hose is used and 30 minutes if a small hose is Used. At these constant rates, how many minutes will it take to fill the pool when both hoses are used simultaneously?
A. 10
B. 12
C. 15
D. 25
E. 50
Mitch, as usual, is spot on .... just adding one thing here -where did that 60 come from? - The volume assumed should be such a number which is a multiple of both 20 and 30,i.e. a common multiple of 20,30.GMATGuruNY wrote:Let pool = 60 liters.cveluswamy wrote:At a constant Rate of flow, it takes 20 minutes to fill a swimming pool if a large hose is used and 30 minutes if a small hose is Used. At these constant rates, how many minutes will it take to fill the pool when both hoses are used simultaneously?
A. 10
B. 12
C. 15
D. 25
E. 50
Rate for large hose = w/t = 60/20 = 3 liters per minute.
Rate for small hose = w/t = 60/30 = 2 liters per minute.
Combined rate for both hoses working together = 3+2 = 5 liters per minute.
Time for both hoses to fill the pool = w/r = 60/5 = 12 minutes.
The correct answer is B.
