Question

Pipe A fills a tank of $700$ litres capacity at the rate of $40$ litres a minute. Another pipe B fills the same tank at the rate of $30$ litres a minute. A pipe at the bottom of the tank drains the tank at the rate of $20$ litres a minute. If pipe A is kept open for a minute and then closed and pipe B is kept open for a minute and then closed and then pipe C is kept open for a minute and then closed and the cycle repeated, how long will it take for the empty tank to overflow?

• A. $42$ minutes
  
• B. $30$ minutes
• C. $12$ minutes
• D. $4$ minutes

Answer 1

The correct option is A $42$ minutes

In 3 Minutes Volume Supplied

$\Rightarrow 40L+30L-20L=50L$

So, In 1 Minute Volume Supplied will be

$\Rightarrow \frac{50L}{3}$

Time Taken to Fill The tank Completely

$\Rightarrow \frac{700L}{\frac{50L}{3}}=42mins$

Therefore Answer is $42mins$