Problem Solving-Variables

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jd6199
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Topic: Problem Solving-Variables
PostSat Jan 20, 2007 12:23 pm
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 Lap   Why a timer is critical to improving your score
SOURCE: PEARSON PRACTICE TEST 1

THE NUMBER OF STAMPS THAT KAYE AND ALBERTO HAD WERE IN THE RATIO OF 5:3 RESPECTIVELY. AFTER KAYE GAVE ALBERTO 10 OF HER STAMPS THE RATIO BECAME 7:5. AS A RESULT OF THIS GIFT KAYE HAD HOW MANY MORE STAMPS THAN ALBERTO?

A.20
B.30
C.40
D.60
E.90

CORRECT ANSWER IS C. HOW TO CALCULATE?
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g2000
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PostSat Jan 20, 2007 10:28 pm
Let A be the number of stamps Alberto has and K be the # stamps Kaye has.

K/A = 5/3
(K-10)/(A+10) = 7/5

Solve this equation for A and K and get A=90 and K=150

That's the number before the gift.
After the gift
A = A + 10 = 90 + 10 = 100
K = K - 10 = 150 - 10 = 140

How many more?
140-100 = 40
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