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| Math Central | Quandaries & Queries |
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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
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