Hours required

Volume of the tower = π5²*8m³ = 200π³
Since it's 3/4 full, amount of water in it = 200*(3/4) = 150πm³

Two things happening:

1. Every minute you are draining (0.08-0.03) = 0.05πm³ of water
Therefore, every hour you are draining 60*0.05 = 3πm³ of water
2. Every hour you drain an additional 4πm³ of water

So, each hour the total drainage is 7πm³ of water

To drain the entire tower it will take you 150/7 hours = 21 3/7 hours or appx 21 hours and 26 minutes.

ashis979 wrote:Volume of the tower = π5²*8m³ = 200π³
Since it's 3/4 full, amount of water in it = 200*(3/4) = 150πm³

Two things happening:

1. Every minute you are draining (0.08-0.03) = 0.05πm³ of water
Therefore, every hour you are draining 60*0.05 = 3πm³ of water
2. Every hour you drain an additional 4πm³ of water

So, each hour the total drainage is 7πm³ of water

To drain the entire tower it will take you 150/7 hours = 21 3/7 hours or appx 21 hours and 26 minutes.

i agree till 'each hour the total drainage is 7πm³ of water' part..

But after this.


total volume = 150πm³

So at 7 πm³ rate 147 πm³ will be drain in 21 hours. But the remainng 3 πm³ will also take 1 hour(because the other drain of 4 πm³ hppens only at the end of the hour) to drain. So, total time wil be 22.

Oh you're right jaxis! Completely forgot about the adding and draining that's going on every minute for the last part.
Been a while...thank god I don't have to worry about the gmat anymore!