Bunuel
A collection of 33 coins amounts to $4.35 in face value. If the collection consists of only dimes and quarters, how many dimes are in the collection? (Dime = 10 cents and quarter = 25 cents)
A. 7
B. 14
C. 25
D. 26
E. 27
Let D = the NUMBER of dimes
So, 10D = the VALUE of the dimes (in cents)
Let Q = the NUMBER of quarters
So, 25Q = the VALUE of the quarters(in cents)
The collection amounts to $4.35 in face value. In other words, the VALUE of the coins is 435 cents.
So we can write: 10D + 25Q = 435
Make our calculations easier let's simplify this equation by dividing both sides by 5 to get:
2D + 5Q = 87 The collection consists of 33 coins In other words, the total NUMBER of dimes and quarters = 33
We can write:
D + Q = 33How many dimes are in the collection? In other words, what is the value of D?
We presently have the following system of equations:
2D + 5Q = 87D + Q = 33Multiply both sides of the bottom equation by 5 to get:
2D + 5Q = 875D + 5Q = 165Subtract the top equation from the bottom equation to get: 3Q = 78
Solve: Q = 78/3 = 26
Answer: D