Kelvin has 36 coins, all nickels and quarters. The total value of all these coins is 3.80. How many nickels does he have

Answer 1

Let n= number of nickels

Let q= number of quarters

Let .05=value of each nickel

Let .25=value of each quarter

My two equations

n+q=36 coins

.05n+.25q= 3.80 using the number and value of each denominations

By substitution q=36-n

so now I have one variable instead of two and I can solve for the number of nickels.

.05n+.25(36-n)=3.80

.05n+9-.25n=3.80

-.20n+9=3.80

-.20n=-5.20

divide each side by .-.20

n=26

to check 26x.05=1.30

and 10x.25= 2.50 because I had 36 coins total 26 nickels and 10 quarters

1.30 and 2.50=3.80