Question

A rectangular tank measuring 80cm by 60cm by 30cm is completely filled with water. A tap was turned on to drain water from the tank at a rate of 9 litre per minute. How long did it take to drain 3/4 the amount of water from the tank?

Answer 1

It will take twelve minutes
first we must find the volume of the tank
so that would be
$v = lwh$

we know that the dimensions are 80x60x30
so the result will be of 144,000 cu.cm
now we need to covert this volume of water to liters
$1000cu.cm = 1l$
by using this formula we can convert the 144,000cu.cm of water to litre
that would be 144,000/1000=144liters
now we know that the tank is draining at the same rate as the new water which is is getting filled in
so know we just need to find the 3/4 of our volume of water
so( 3/4)144= 108litres
we know that the pipe is filling the tank at a rate of 9litres per minute
so now to find the time it take we just need to divide the 108 litres by 9
which give us a time rate of 12 mins

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