Q9 of 79 Page 244

Through a cylindrical pipe of internal radius 7 cm, water flows out at the rate of 5 cm/sec. Calculate the volume of water (in litres) discharged through the pipe in half an hour.

We need to find volume of water (in liters) discharged through the pipe in half an hour.


Half an hour = 30 minutes


Let us change minutes into seconds. For that we have to multiply 30 by 60. Because 60 seconds = 1 minute.


⇒ 30 60 = 1800 seconds.


Volume of water discharged in half an hour = r2 5 1800


= (7)2 5 1800


= 7 7 5 1800


= 22 7 5 1800


= 1386000 cubic cm ()


= (1000 cm3 = 1 liter)


= 1386 liters


Volume of water discharged through the pipe in half an hour is 1386 liters.


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