Brain Teasers
Will He Make It?
Gino's mom has told him he needs to take a bucket of water over to their neighbor since she is experiencing problems with her water supply. He doesn't want to waste much time since he has a soccer game to play later in the afternoon. From past experience he knows if he uses the small hose it takes 45 minutes to fill the bucket with water. He also knows that the larger hose can do the same in 30 minutes. If he uses both hoses, how long will it take him to fill the bucket?
Answer
The small hose can fill 1/45 of the bucket every minute. The larger hose can fill 1/30 of the bucket every minute. To add the two speeds, we need to first find a common denominator.1/45 = 2/90 and 1/30 = 3/90
Adding the two speeds:
2/90 + 3/90 = 5/90 = 1/18
Since both hoses together can fill 1/18 of the bucket every minute, it will take 18 minutes. By doing this Gino will save at a minimum 12 minutes. This will get him to his soccer game just in time.
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Comments
How big of a bucket are we talking here!!!
I think its impossible to say because the teser doen't say how many litres of water the bucket takes. am I wrong?
I don't think it matters how big, or the liters, but the hose,and how long it took to fill the bucket Great one. although I guessed 15 minutes
Nov 02, 2005
That is so old. It is a good brain teaser but lots of people know it and the answer is 18 like i thought
Gotta give it to you, was lost in my train of thoughts. Gud one!!
You can also do (1/30)x + (1/45)x = 1 and solve for x (the minutes)
I too used Michelle's method. It's an easy one, but I think this guy's real problem is his water pressure. Better get a new well pump!
WHAT A GREAT TEASER BUT I THINK THAT THE PROBLEM IS HOW MUCH OF THE ATER PRESSURE HE HAS GOT....i ALSO USED MICHAELL'S METHOD IT WAS A GOOD THAT I HAVE SEEN YET.....
ehhh, alright teaser
I did it very quickly in my head by recognizing that the ratio between the hoses is 2::3. This means that the large hose will fill 3/5 of the bucket. 3/5 x 30 = 18.
Suppose the bucket holds 90 litres. The first hose delivers 2 litres per minute. The second hose delivers 3 litres per minute. Together they deliver 5 litres per minute.90/5 = 18 min.
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