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Maggie's savings

by Vemuri » Sun Mar 15, 2009 4:52 am
Maggie pays 1/8 of her monthly income for food, 1/8 for utilities, 1/8 for student loans, and 4/5 of the reminder for rent. If at the end of each month Maggie puts 1/2 of her remaining income into a CD account, what portion of Maggie's monthly income does she put into the account?

A. 1/8
B. 1/10
C. 7/80
D. 1/16
E. 1/20
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by DanaJ » Sun Mar 15, 2009 4:59 am
She spends 3/8 of her income, x, on food, student loans and utilities, meaning that she has 5/8 left. Of this, she spends an additional 4/5 on rent, meaning that, after paying rent, she's left with 1/5 of 5/8x or 1/5*5/8x = 1/8x.
Out of this 1/8x, she then saves 1/2: this makes her savings 1/2*1/8x = 1/16x.

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by PAB2706 » Sun Mar 15, 2009 6:32 am
i dnt understand...why have u taken 1/5th(1-4/5). they have said 4/5th of the remainder. If 5/8 is remaining after paying for food etc...shudnt the rent money be 4/5 ( 5/8) ...??


I am confused in understanding the wording of the problem maybe..
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by DanaJ » Sun Mar 15, 2009 7:22 am
Yes, the rent money will be 4/5 * 5/8, but then she's left with 1/5 (or 1 - 4/5, as you have pointed out) of 5/8. It's this part of her income that gets split into two, and one of the two halves goes into the savings account. That's why 1/5*5/8*1/2 = 1/16 will be the answer.
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by cramya » Sun Mar 15, 2009 9:06 am
1/8+1/8+1/8 = 3/8

Remaining = 1- 3/8 = 5/8

4/5 of this remaining 5/8 on rent = 4/5*5/8
= 1/2

Total amt spent = 3/8+1/2 = 7/8

Remaining = 1 - 7/8 = 1/8


1/2 of this remaining 1/8th is saved to CD = 1/2*1/8 = 1/16


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CR
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Re: Maggie's savings

by Stuart@KaplanGMAT » Sun Mar 15, 2009 10:08 am
Vemuri wrote:Maggie pays 1/8 of her monthly income for food, 1/8 for utilities, 1/8 for student loans, and 4/5 of the reminder for rent. If at the end of each month Maggie puts 1/2 of her remaining income into a CD account, what portion of Maggie's monthly income does she put into the account?

A. 1/8
B. 1/10
C. 7/80
D. 1/16
E. 1/20
Picking numbers is almost always the easiest way to solve this type of question.

Looking at the fractions in the question, we have 8ths, 5ths and halves. $80 seems like a good easy number to work with (we also note that all the denominators in the answers are factors of 80).

So, we've spent:

1/8 = 10 on food
1/8 = 10 on utilities
1/8 = 10 on student loans

so $30 so far, leaving us with $50.

We now spend 4/5 of the remainder on rent: (4/5)(50) = 40

We have $10 left over. We put 1/2 of that, i.e. $5, into a CD account.

Therefore, we've put $5/$80 into the account.

5/80 = 1/16: choose (D)
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by shibal » Thu Mar 19, 2009 4:14 am
by far picking numbers is the best way to solve this kind of question.... the trick here is that they say 4/5 of the remaining... if u rush u may think it's 4/5 of x... the rest is pretty straight forward...

i simply love this kind of question, easy and quick to solve and is considered an upper medium level (that's what i read around some books and forum)
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