A coin bank has 250 coins, dimes and quarters, worth $39.25. How many of each type of coin are there?

1 answer

Let's denote the number of dimes as \( d \) and the number of quarters as \( q \).

We have the following two equations from the problem statement:

  1. The total number of coins: \[ d + q = 250 \]

  2. The total value of the coins (in cents): \[ 10d + 25q = 3925 \] (Note: The value in dollars is converted to cents for easier calculations.)

Now we can solve these equations step-by-step.

From the first equation, we can express \( q \) in terms of \( d \): \[ q = 250 - d \]

Next, we substitute \( q \) into the second equation: \[ 10d + 25(250 - d) = 3925 \]

Expanding the equation: \[ 10d + 6250 - 25d = 3925 \]

Combining like terms: \[ -15d + 6250 = 3925 \]

Now, let's isolate \( d \): \[ -15d = 3925 - 6250 \] \[ -15d = -2325 \]

Dividing both sides by -15: \[ d = \frac{2325}{15} = 155 \]

Now that we have \( d \), we can find \( q \): \[ q = 250 - d = 250 - 155 = 95 \]

Thus, the number of dimes is \( d = 155 \) and the number of quarters is \( q = 95 \).

Let's summarize:

  • Number of dimes: 155
  • Number of quarters: 95

We can double-check the values:

Calculating the total value:

  • Value from dimes: \( 155 \times 10 = 1550 \) cents
  • Value from quarters: \( 95 \times 25 = 2375 \) cents
  • Total value: \( 1550 + 2375 = 3925 \) cents (which corresponds to $39.25)

Everything checks out correctly. Therefore, the solution is:

  • Dimes: 155
  • Quarters: 95