Answer:
= 3.65.
Step-by-step explanation:
You know that Tom has 23 coins in total. That means the number of dimes and the number of quarters equals 23.
D + Q = 23
You also know that the total value of the coins is $3.65. A dime is worth $0.10 and a quarter is worth $0.25, so:
0.10*D + 0.25*Q = 3.65
That says that 10 cents per dime times the number of dimes, plus 25 cents per quarter times the number of quarters is three dollars and sixty-five cents.
So you have a system of linear equations:
D + Q = 23
0.10D + 0.25Q = 3.65
I'm going to multiply the bottom row by 100 to clear the decimals.
D + Q = 23
10D + 25Q = 365
Now I can multiply the top row by -10 to eliminate the D terms
-10D - 10Q = -230
10D + 25Q = 365
________________
0D + 15Q = 135
15Q = 135
Q = 9
Tom has 9 quarters.
If D + Q = 23, and Q = 9, then:
D + 9 = 23
D = 14
Tom has 14 dimes.
Always good to double check:
9 quarters is worth $2.25. 14 dimes is worth $1.40. These should sum to $3.65.
2.25 + 1.40
