​A tank can be filled by 5 pipes in 80 minutes. How long will it take to fill the tank by 8 pipes of same dimensions? ​

Correct option is A

Given:

5 pipes can fill the tank in 80 minutes. 

Solution:

If 5 pipes take 80 minutes, then the rate for 1 pipe would be 5 times slower.

Time for 1 pipe = 80×5 = 400 minutes 

Since 8 pipes will fill the tank 8 times faster than 1 pipe: 

Time for 8 pipes = $$\frac{400}{8}$$ = 50 minutes

​It will take 50 minutes for 8 pipes to fill the tank.

Thus, correct answer is (a) 50 minutes