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06 Nov 2018, 23:47
Kudos
Bookmarks
D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
5%
(low)
Question Stats:
84% (00:42) correct
16%
(00:34)
wrong
based on 105
sessions
History
Date
Time
Result
Not Attempted Yet
If \(2x − y = 10\) and \(\frac{x}{y} = 3\), then x =
A. − 10
B. 2
C. 4
D. 6
E. 12
A. − 10
B. 2
C. 4
D. 6
E. 12
07 Nov 2018, 03:42
Kudos
Bookmarks
Bunuel
Given ,
x/y = 3
x = 3y.
Now
2x - y = 10
2*3y - y = 10
5y= 10
y = 2.
x= 3y = 3*2 = 6.
The best answer is D.
07 Nov 2018, 08:10
Kudos
Bookmarks
Bunuel
I'd typically use the approach that selim used.
However, another approach is to test the answer choices
We can also use some number sense to help us determine which answer choices to test first.
Notice that we're told x/y = 3
So, if answer choice A were correct, we'd get -10/y = 3, in which case y is some fraction.
Now if x is an integer (-10) and y is some fraction, we can see that these values for x and y will not satisfy the other equation, 2x - y = 10
So, let's start testing answer choices (possible x-values) that yield "nicer" values of y when we solve the equation x/y = 3
Answer choice B is no good, because we get 2/y = 3, which will yield a fraction value for y.
Answer choice C is no good, because we get 4/y = 3, which will yield a fraction value for y.
Answer choice D is promising, since we get 6/y = 3, which means y = 2
Good so far!
So, x = 6 and y = 2 satisfies the equation x/y = 3, but does it satisfy the other equation, 2x - y = 10?
When we plug in those values, we get: 2(6) - 2 = 10, PERFECT!
So, x = 6 and y = 2 satisfies BOTH equations
Answer: D
Cheers,
Brent
