A total of 20 quarters and nickels add up to $4.00. How many nickels are there?

5 nickels

Step-by-step explanation:

You can setup and solve a system of equations, or you can solve by trial and error until you get the correct answer.

Here is the solution by trial and error.

If all 20 coins are quarters, the value is 20 * $0.25 = $5

That is too much value.

Let's try 16 quarters. 16 quarters are worth 16 * $0.25 = $4.

That is the correct value, but it is only with quarters, and only 16 of them.

We need fewer quarters than 16.

Try 12 quarters: 12 * $0.25 = $3.00

The number of nickels is: 20 - 12 = 8

8 nickels are worth 8 * $0.05 = $0.40

12 quarters and 8 nickels are worth $3.00 + $0.40 = $3.40

There are 20 coins, but the value is too low.

The number of quarters is between 12 and 16.

Try 14 quarters and 6 nickels:

14 * $0.25 + 6 * $0.05 = $3.50 + $0.30 = $3.80

We are closer to $4 but not there yet.

Try 15 quarters and 5 nickels.

15 * $0.25 + 5 * $0.05 = $3.75 + $0.25 = $4

The total value is $4 and there are 20 coins. This is the answer.

15 quarters and 5 nickels works.

Answer: 5 nickels