anujtsingh wrote:
In assembling a Bluetooth device, a factory uses one of two kinds of modules. One module costs $6.25 and the other one, that is cheaper, costs $2.50. The factory holds a $70 worth stock of 22 modules. How many of the modules in the stock are of the cheaper kind?
(A) 4
(B) 8
(C) 12
(D) 16
(E) 18
We can also solve the question using ONE VARIABLE.
Let x = the number of cheap modules
So, 22 - x = the number of expensive modules
So, the VALUE of the cheap modules = 2.5x
So, the VALUE of the cheap expensive = 6.25(22 - x)
The TOTAL value = 70 dollars, so we can write: 2.5x + 6.25(22 - x) = 70
Expand to get: 2.5x + 137.5 - 6.25x = 70
Simplify: -3.75x + 137.5 = 70
Rearrange to get: -3.75x = -67.5
Solve: x = 18
Answer: E
Aside: Here's a free video on deciding how many variables to assign on questions like this:
http://www.gmatprepnow.com/module/gmat- ... /video/906 Cheers,
Brent
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