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by candygal79 » Mon Mar 24, 2014 3:35 am
Marv earned in two consecutive days a total of 920 dollars. Half of the amount that Marv earned on the first day is 20 dollars less then the amount that he earned on the second day. How much did Marv make on the first day (in dollars)?

A-540 B-200 C-600 D-700 E-640
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by Brent@GMATPrepNow » Mon Mar 24, 2014 4:57 am
candygal79 wrote:Marv earned in two consecutive days a total of 920 dollars. Half of the amount that Marv earned on the first day is 20 dollars less then the amount that he earned on the second day. How much did Marv make on the first day (in dollars)?

A-540 B-200 C-600 D-700 E-640
A fast approach here is to plug in the answer choices until you find the one that meets the given conditions.

Alternatively, we can use algebra.

Let x = $ earned on 1st day.

Half of the amount that Marv earned on the first day is 20 dollars less then the amount that he earned on the second day.
So, x/2 + 20 = $ earned on 2nd day.

Marv earned in two consecutive days a total of 920 dollars
So, x + (x/2 + 20) = 920
Eliminate fractions by multiplying both sides by 2 to get: 2x + x + 40 = 1840
Simplify: 3x + 40 = 1840
Subtract 40 from both sides: 3x = 1800
Solve: x = 600

Answer: C

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by GMATGuruNY » Mon Mar 24, 2014 5:03 am
candygal79 wrote:Marv earned in two consecutive days a total of 920 dollars. Half of the amount that Marv earned on the first day is 20 dollars less then the amount that he earned on the second day. How much did Marv make on the first day (in dollars)?

A-200 B-540 C-600 D-640 E-700
We can PLUG IN THE ANSWERS, which represent the amount earned on the first day.
I've reordered the answer choices so that they are in ascending order.
Let F = first-day earnings and S = second-day earnings.
When the correct answer choice is plugged in, half of F will be equal to 20 less than S.

Answer choice C: F = 600
Half of F = 600/2 = 300.
S = total - F - 920-600 = 320.
Success!
Half of F is equal to 20 less than S.

The correct answer is C.
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by Abhishek009 » Mon Mar 24, 2014 9:53 am
candygal79 wrote:Marv earned in two consecutive days a total of 920 dollars.
a + b = 920
candygal79 wrote:Half of the amount that Marv earned on the first day is 20 dollars less then the amount that he earned on the second day.
a / 2 = b - 20

a = 2b - 40
candygal79 wrote: How much did Marv make on the first day (in dollars)?
We already know as a + b = 920

Substitute a = 2b - 40

2b - 40 + b = 920

3b = 960

b = 320

So , a = 2b - 40

Or, a = 2*320 - 40

Hence a = 640 - 40

Or ,[spoiler] a = 600[/spoiler]
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