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What is the answer to the math question in the movie?

posted 9 years ago by Loverly_outcast
5 replies | jump to latest

Here is the riddle: We have a bathtub that can hold 100 gallons of water. If "A" can fill it at a rate of 20 gallons per minute and "B" can fill at a rate of 10 gallons per minute and there is a hole ing the tub which drains the water at a rate of 5 gallons per minute, how long will it take to fill the tub??

I asked my physics teacher and math professor, they say you can't solve it due to the lack of data.

My top 50: http://www.imdb.com/list/ls038441044/

[–] ivgaba 9 years ago

Lack of data? Why? It is extremely simple math. Every minute you can fill the tub A + B - C (drainage) gallons, so 20 + 10 - 5 = 25 gallons per minute. If the tub can hold 100 gallons, it will fill up in 4 minutes (100/25).

You sure your teachers weren't pulling your leg?

[–] Underdog_73 8 years ago

It wasn't a riddle. It was a mathematical calculation. And a simple one at that. All the necessary data is provided. No intelligent teacher seriously claimed otherwise.

As the other poster said, the answer is 4 minutes. A 100 gallon tub is filled at a rate of 30 gallons (20+10) per minute and drains at a rate of 5 gallons per minute. As a result, it's filling at a rate of 25 gallons per minute. 25 goes into 100, 4 times. 4 minutes to get 100 gallons.

[–] jtrichey13 8 years ago

No, the answer is infinity because that water keeps draining out of that pesky hole at 5 gallons a minute. It will never be truly filled. ;)

Downwards is the only way forwards.

[–] jriley555 (8386) 7 years ago

nope- as long the entire volume of the tub is occupied by water, it doesnt matter how much is coming in or going out.

you are over-interpreting the meaning of the word 'full'

[–] Moonglum9 (11320) 7 years ago

Yeah, once you hit that four minute mark, you will have a continually full tub of 100 gallons where it loses 5 gallons through the hole each minute and the excess 25 gallons spilling out from the top until someone shuts off the water.