Question

There is a cuboidal tank whose length, breadth and height are 15 m, 28 dm and 6 m respectively. 75% of the tank's water need to be pumped out, find the total time taken (in hours) to pump out the required amount of water through a tap that can pump out 7 litres of water per minute.
1. 300
2. 350
3. 400
4. 450

Answer 1

Correct Answer - Option 4 : 450

Given :

Length, breadth and height of the tank are respectively 15 m, 28 dm and 6 m 

75% of the whole volume need to be taken out of the tank 

Outlet tap can pump out 7 litres of water per minute

Formula used :

The total volume of the cuboid = length × breadth × height

Total time taken to pump out water = Total volume/Water thrown out per unit time  

Calculations :

Volume of the cuboid = 15 ×  2.8 × 6    (1 dm = (1/10) m)

⇒ 252 m³ or 252000 litres                 (1 m3 = 1000 litres)

Now 75% of the total volume = 75% of 252 m³

⇒ 189 m³ or 189000 litres              

Total time taken to pump out 75% of the water = 189000/7 

⇒ 27000 minutes 

Total time in hours = (1/60) × 27000 

⇒ 450 hours 

∴ total time taken to pump out 75% of the water is 450 hours