BTGmoderatorDC wrote:A collection of 16 coins, each with a face value of either 10 cents or 25 cents, has a total face value of $2.35. How many of the coins have a face value of 25 cents?
A) 3
B) 5
C) 7
D) 9
E) 11
OA B
Source: Official Guide
Let
D = the NUMBER of 10-cent coins
Let
Q = the NUMBER of 25-cent coins
Notice that the VALUE of
Q 25-cent coins = ($0.25)
Q
For example, the VALUE of
six 25-cent coins = ($0.25)
6 = $1.50
And the VALUE of
ten 25-cent coins = ($0.25)
10 = $2.50
etc
Likewise, the VALUE of
D 10-cent coins = ($0.10)
D
The collection has 16 coins
We can write:
D +
Q = 16
The collection has a total value of $2.35
So, (0.10)
D + (0.25)
Q = 2.35
So, we have the following system:
(0.10)
D + (0.25)
Q = 2.35
D +
Q = 16
Take the top equation and multiply both sides by 10 to get:
D + 2.5
Q = 23.5
D +
Q = 16
Subtract the bottom equation from the top to get:
1.5Q = 7.5
Solve: Q = 5
Answer: B
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
