Question

A person has 20 coins consisting of dimes and quarters. If the total amount of money is $3.35, how many quarters are there

Answer 1

Let q represent the number of quarters. Then 20-q is the number of dimes. The money total is

... 25q +10(20-q) = 335

... 15q +200 = 335

... 15q = 135

... q = 135/15 = 9

The person has 9 quarters.