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mixture

by ketkoag » Wed Jun 10, 2009 11:31 am
80 A and 20 B are mixed together. By removing some A, the remaining A will be 75% of the mixture. How many A must be removed?
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by ssmiles08 » Wed Jun 10, 2009 11:38 am
If 80 ml of A and 20 ml of B are mixed together: 100 ml total

x ml of A is taken out.

80-x = remaining A

% of A in new mixture is 0.75*(100-x)

so 80 - x = 75 - 0.75x

5 = (1/4)*x

x = 20ml

so amount of A removed is 20ml.

Hope I am not missing anything.
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by tohellandback » Wed Jun 10, 2009 7:58 pm
do these types with reasoning and you will save a lot of time.
total mixture is 100. A-80 and B-20
in the remaining mixture, A is 75% so B is 25% i.e. total mixture must be 80
the loss in mixture is because A was taken out.. 20 As must have been removed
The powers of two are bloody impolite!!
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