SEARCH HOME
 Math Central Quandaries & Queries
 Question from val, a student: I would like help working out a math word problem. A collection of 30 coins worth $5.50 consists of nickels, dimes, and quarters. There are twice as many dimes as nickels. How many quarters. Could you teach me how to find this formula? Hi Val, I would start by letting n be the number of nickels, d the number of dimes and q the number of quarters. You are told that the number of coins is 30 so n + d + q = 30. The value of the 30 coins is$5.50 but I would rater work in cents so the value of the 30 coins is 550¢. Each nickel is worth 5¢, each dime 10¢ and each quarter 25¢ so

5n + 10d + 25q = 550.

The final piece of information is that there are twice as many dimes as nickels so

d = 2n.

Substitute 2n for d in each of the first two equations. This gives you two equations in n and q. Solve them for n and q.

I hope this helps,
Penny

Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.