Question 1196702
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The response from the other tutor shows the setup for solving the problem by the standard method for "mixture" problems.  Of course you want to use a method something like that if a formal algebraic solution is required.<br>
But in problems like this where the numbers are "nice" -- as they are in this problem -- a quick and easy solution can be obtained by seeing where the percentage of the mixture lies between the percentages of the two ingredients.<br>
Look at the three percentages (on a number line, if it helps) and observe/calculate that 69 is 44/55 = 4/5 of the way from 25 to 80.  That means 4/5 of the mixture needs to be the 80% ingredient.<br>
Since the mixture is to be 10 ml, that means using 8 ml of the 80% sugar solution and 2 ml of the 25% sugar solution.<br>
ANSWER: 8 ml of the 80% solution; 2 ml of the 25% solution<br>
CHECK:
.80(8)+.25(2) = 6.4+.5 = 6.9
.69(10) = 6.9<br>
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Postscript....<br>
If this method of solving the problem looks like magic, observe that the formal solution from the other tutor arrives at that same fraction 44/55 for the fraction of the mixture that must be the 80% sugar solution....<br>