If x + y = 24 and 2x-7y=15, which of the following is equal to 13?
A. x-y
B. x+y
C. x-2y
D. 2x + y
E. 2x-y
[spoiler][C][/spoiler][/spoiler]
Through either substitution or combination I can get to the right answer, but it involves several sort of messy fractions and was thus somewhat time consuming...any experts have a faster method?
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bryan22583
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rintoo22
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Simultaneous eq can give you the value of x and y. I did the problem myself and realised that I must keep the values in fraction. So dont simplify it further.If x + y = 24 and 2x-7y=15, which of the following is equal to 13?
Then substituting the value of x and y in each equation should get you the answer.
x + y = 24 and 2x-7y=15.... (1)
x = 183/9
y = 33/9
Just a glance through the options should suggest that C should be the answer. Substitute the values and confirm the result.
Important points in my opinion are
1. Leave the values of x and y as fraction
2. Substitue the values after going through the options.
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Anju@Gurome
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We have to make 13 from 24 and 15.bryan22583 wrote:If x + y = 24 and 2x-7y=15, which of the following is equal to 13?
Note that (24 + 15) = 39 = 3*13
Hence, if we add multiply each of the given equation by 1/3 and add them, we will get the correct answer.
So, (x + y)/3 + (2x - 7y)/3 = 13
--> (x/3 + 2x/3) + (y/3 - 7y/3) = 13
--> x - 2y = 13
The correct answer is C.
Anju Agarwal
Quant Expert, Gurome
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GMATGuruNY
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Adding together x+y = 24 and 2x-7y = 15, we get:bryan22583 wrote:If x + y = 24 and 2x-7y=15, which of the following is equal to 13?
A. x-y
B. x+y
C. x-2y
D. 2x + y
E. 2x-y
(x+y) + (2x-7y) = 24+15
3x - 6y = 39.
Dividing each side by 3, we get:
x - 2y = 13.
The correct answer is C.
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I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
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