Suzette and Marlene are sisters. 10 years ago, Marlene was 3

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Suzette and Marlene are sisters. 10 years ago, Marlene was 3 [#permalink]

15 Oct 2005, 08:33

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Suzette and Marlene are sisters. 10 years ago, Marlene was 3
times as old as Suzette. 5 years ago, Marlene was twice as
old as Suzette. How old will Suzette be in 6 years?

A. 31
B. 15
C. 25
D. 21
E. 35

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15 Oct 2005, 08:50

M-10 = 3(S-10) --> M-10 = 3s -30 --> M = 3s-20 --(1)
M-5 = 2(S-5) --> M-5 = 2s-10 --> M = 2s - 5 -----(2)

S+6 = ??

Equating 1 and 2,

3s - 20 = 2s - 5
s = 15

s + 6 = 21 (D)

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15 Oct 2005, 11:01

OA is D and here is the detailed explanation:

This problem can be solved algebraically. With the information given about Suzette (S) and Marlene (M), we can set up the following equations:

(S - 10)3 = M - 10
(S - 5)2 = M - 5

As you can tell, this problem will involve solving two linear equations with two unknowns. One way to solve this problem is to express one of the unknowns in terms of the other. So, in this problem:

(S - 10)3 = M - 10
3S - 30 = M - 10
M = 3S - 20

Now that we can substitute the expression of M into the next equation. We will then be able to solve for Suzette's age:

(S-5)2 = 3S - 20 - 5
2S - 10 = 3S - 25
2S + 15 = 3S
S = 15

Now we know that Suzette is 15. In 6 years, she will be 21.

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Re: PS: Ages [#permalink]

15 Oct 2005, 11:08

sudhagar wrote:

Sorry for the crude diagram - hopefully you'll make something out of it

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crud.JPG [ 10.22 KiB | Viewed 135 times ]

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15 Oct 2005, 11:19

Two equations, two variables.

Late, but D.

[#permalink] 15 Oct 2005, 11:19

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Suzette and Marlene are sisters. 10 years ago, Marlene was 3

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Suzette and Marlene are sisters. 10 years ago, Marlene was 3

Suzette and Marlene are sisters. 10 years ago, Marlene was 3

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