Question

Two pipes can fill a tank in 10 hours and 12 hours, respectively. While a third pipe can empty the full tank in 20 hours. If all the three pipes operate simultaneously, in how much time the tank filled?

• A. 7 hours 30 minutes
• B. 6 hours 40 minutes
• C. 8 hour 30 minutes
• D. None of these

Answer 1

The correct option is A 7 hours 30 minutes

Here, x = 10, y = 12 and z = -20
$\therefore$ The tank will be full in

$=\left(\frac{x\times y\times z}{xy-yz-zx}\right)hours$

$=\left(\frac{10\times 12\times -20}{10\times 12-12\times 20-20\times 10}\right)hours$

$=\left(\frac{15}{2}\right)hoursor,7hours30minutes$