A rectangular water tank is 80 m x × 40 m. Water flows into it through a pipe of 40 sq.cm at the opening at a speed of 10 km/hr. The water level will rise in the tank in half an hour is
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Correct answer: D
Explanation
The correct option is 4.
given rectangular water tank is 80 m x × 40 m
volume of rectangular water tank = volume of water filled by the pipe (area of pipe × speed of flow of water)
volume of rectangular water tank = 8000 x × 4000 {∵ 80 m = 8000 cm , 40 m = 4000 cm}
8000 x × 4000 = 40 × 10 × 1000 × 100 {1km = 1000m, 1m = 100cm}
x = 
{ height raised in 1 hr}
height raised in 30 mins = 