Step 1: Suppose Ann is A year old, and Ben is B year old now.
We will analyze the problem "backward".
Step 2: Start with the last phrase "When Ben was 3 times as old as Ann". If Ann was x-year-old, then Ben would be 3x at that time.
Step 3: Consider the phrase before the last. "when Ann is three times as old as Ben was". This means Ann will be 3(3x) = 9x year old.
Therefore, Benn will be 3x + (9x - x) = 11x year old at that time. (In deed, Ben's age here doesn't matter.)
Step 4: "when Ben was half as old as Ann will be". This means Ben was 9x/2 year old. Therefore, Ann was (9x/2 - 3x) + x = 5x/2 year old at that time.
Step 5: "Ben is twice as old as Ann was". This means Ben is 2(5x/2) = 5x year old now.
The chart below illustrates the problem:
Step 1, Step 2, Step 3, Step 4, Step 5
Name: Age now, Age was, Will be, Was, Now
Ann: A, x, 9x, 5x/2,
Ben: B, 3x, (11x), 9x/2, 5x
Three equations are obtained from the chart.
Ben's current age: B = 5x
Total of Ann and Ben's current ages: A + B = 56
(Difference of Ann's ages between Step 1 & 2) = (difference of Ben's ages between Step 1 & 2), that is
A - x = B - 3x
Solve the system of the simultaneous equations for A, B, and x.
B = 5x
A + B = 56
A - x = B - 3x
We have
x = 7
A = 3x = 21 (Ann)
B = 5x = 35 (Ben)
2007-10-14 16:44:51
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answer #1
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answered by rj 2
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I suppose the other person (who has only negative points I notice - how d'ja do that?) was correct. My answer refers to your name - why the extra /n/ in the word greeneggsandNham?? Typo??
2007-10-11 01:07:30
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answer #2
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answered by thisbrit 7
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