🚀 go-pugleaf

In article <7g44k5$ggv$1@nobel2.pacific.net.sg>, "Anthony Teo"
<shepherdmoons@pacific.net.sg> wrote:

> Hi...
> 
> I've got 2 questions which r bugging me alot...if u know how to answer them
> please reply back to me : shepherdmoons@pacific.net.sg
> 
> 1. A cistern can be filled by two pipes in 6 minutes. If the larger pipe
> takes 5 minutes less than the smaller pipe to fill the cistern, find the
> time in which the cistern could be filled by each of the pipes.
> 
> 2. An oil tanker can be filled by two pipes in 12 hours. The larger pipe
> alone takes 10 hours less than the smaller one alone. Find the time taken by
> the larger pipe to fill the tanker.
> 
> 
> Anthony

These are both the same problem with different units and different
numbers. They also involve ratios. A careful examination might tell you
something about how the ratios in the two problems are related and save
you some effort on the second solution.

Make and test some guesses. This is a problem solving strategy called
'guess and check,' taught in elementary schools, but often forgotten by
older students. The strategy tells you to make a guess of (in this case) a
single value--say the length of time it takes the large pipe to fill the
cistern--then check by calculating what the other values would be if the
guessed value is correct.
 
You know that it will take longer than 6 minutes for either pipe to fill
the cistern on its own. 

Suppose it takes 12 minutes for the larger pipe to fill the cistern. Then
how long would it take the second pipe working alone to fill the cistern?
What fraction of the cistern would the large pipe fill on its own in 6
minutes? The small pipe? Do these two fractions add to 1, more than 1 or
less than 1?
 
If the fractions add to 1 (the whole container filled in 6 minutes with
both pipes working together), you have reached a solution. If the sum is
more or less than 1, you need to adjust your guess and try again.
 
Think about what your second result tells you about the adjustment you
made. For example, if two new fractions is closer to 1, you have adjusted
in the right direction. Adjust your guess again and recalculate. Use a
table to keep track of your guesses and the results when you check them. 



BTW, there is a solution, and it is a fairly simple set of numbers. Good
luck on finding it.