Solution:
Let "d" be the number of dimes
Let "n" be the number of quarters
1 dime = $ 0.10
1 nickel = $ 0.05
There are 140 coins in the jar
Therefore,
d + n = 140
n = 140 - d ------- eqn 1
Lee has $10.20 in a jar that contains only nickels and dimes
Therefore,
[tex]d \times 0.10 + n \times 0.05 = 10.20[/tex]
0.1d + 0.05n = 10.20 -------- eqn 2
Substitute eqn 1 in eqn 2
0.1d + 0.05( 140 - d) = 10.20
0.1d + 7 - 0.05d = 10.20
0.05d = 3.2
Divide both sides by 0.05
d = 64
Substitute d = 64 in eqn 1
n = 140 - 64
n = 76
Thus there are 76 nickels in jar
