How many quarters and how many dollar bills does it contain?

Question

A tip jar contains twice as many quarters as dollar bills. If it has a total of $12 in it, how many quarters and how many dollars bills does it contain?

Answer 1

Let x = number of quarters, y = number of dollars. Then, x = 2y (twice as many quarters as dollars). Second equation is:  0.25 x + 1 y = 12.00. Substitute value of x (from first equation) into second equation, thus:

025 (2y) + y = 12.00, then 0.5 y + y = 12.00, then 1.5 y = 12.00. Solve for y--y = 8, so number of dollars is 8. Since x = 2y, x = 2(8) = 16, number of quarters, thus twice the number of dollars.