There are 3 inlet taps and 1 outlet tap with diameters 8, 6, 2 (cms – inlet taps) and 4 cm respectively. The rate of flow of oil is directly proportional to the square of the radius of the tap. It takes 9 minutes for the smallest tap to fill an empty tank. What is the time taken to fill an empty tank when all the taps (inlet + outlet) are kept open?

the answer is similar to this http://wiki.answers.com/Q/How_much_time_is_required_to_fill_a_tank_if_pipe_A_can_fill_it_in_20_minutes_pipe_B_can_fill_it_in_30_minutes_and_pipe_C_can_drain_it_in_40_minutes_and_all_of_the_pipes_are_opened_on_an_empty_tank

shoot i just answered this and lost it somehow!! i've no time to type it now = the answer i got was 9/22 minutes

scroll down for related answers in the link I provided. You should get an idea as to how to approach this problem

could you help how to calcuate the rate of flow

rate of flow is proportional to radius squared so flow rate of tap A = k*8^2 = 64k similarly the flow rates of the other three are 36k, 4k and 16k

Hi, but shouldn't the radius be 4, since diameter is 8

oh you are right. well spotted. so it is 16k, 9k, k and 4k

getting the answer as 18/22, but it seems to be 7/22

total flow = 26-4= 22

hi

total flow rate is 22k per minute. so what is the next step? what is the value of k?

total capacity of the tank is 36 units (2^2*4.5)

total flow that comes is 16+9+1-4==22

ok got it, total 9 units, 9/22

thanks for your help

np. glad you could work it out on your own.

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