Katie has 36 coins in her jar (nickels, dimes, and quarters) totalling $4.20. She has twice as many dimes as quarters. How many nickels does Katie have?

Question

Katie has 36 coins in her jar (nickels, dimes, and quarters) totalling $4.20. She has twice as many dimes as quarters. How many nickels does Katie have?

Answer 1

n = number of nickels

d = number of dimes

q = number of quarters

n + d + q = 36

0.05n + + 0.10d + 0.25q = 4.20

(0)n + d - 2q = 0

You have a system of 3 equations in 3 unknowns, which you can solve by elimination, matrix methods, or Cramer's rule. Using Cramer's rule, I got

n = 12

d = 16

q = 8

Test the solution.