Question

A rectangular water tank is 80 m $\times$ 40 m. Water flows into it through a pipe 40 sq.cm at the opening at a speed of 10 km/hr. By how much, the water level will rise in the tank in half an hour?

• A.
• B.
• C. 1 cm
• D. 5 cm

Answer 1

The correct option is B

Length of water column flown in 1 min. $\left(\frac{10\times 1000}{60}\right)$m = $\frac{500}{3}$m

Volume flow for 30 min $=(30\times \frac{500}{3}\times \frac{40}{100\times 100})$m${}^3$= 20 m${}^3$

$\therefore$Rise in water level $=\left(\frac{20}{40\times 80}\right)m=\left(\frac{1}{160}\times 100\right)cm=\frac{5}{8}cm$