Question

Forty coins, all nickels and dime, all worth $3.15. How many nickels and dimes are there

Answer 1

15 nickels

25 dimes

Explanation:

Letting

x = nickels

y = dimes

We create a system of equations

x + y = 40

0.05x + 0.10y = 3.15

Let's take the first one and subtract the X

y = 40 - x

Now we can substitute that into the second equation

0.05x + 0.10(40-x) = 3.15

0.05x + 4 - .10x = 3.15

0.05x = 0.75

Those last steps were just combining like terms. Now we divide by 0.05

x = 15 nickels

Now we can use the original equation and plug in 15 for x

15 + y = 40

y = 25 dimes