Question

Yoon has a number of dimes and quarters she wants to put into rolls. She has 124 coins in all that add up to $20.50. If a roll of quarters is equal to ten dollars, how many extra quarters does she have that will not fill up a roll?

Answer 1

A) D + Q = 124
B) .10D + .25Q = 20.50

Multiply B) by -4
B) -.40D + -Q = -82.00 then add to A)
A) D + Q = 124

.60 D = 42
D = 70 Dimes
Q = 54 Quarters

A roll of quarters = $10 = 40 Quarters so there will be 14 "extra" quarters.