   SEARCH HOME Math Central Quandaries & Queries  Question from Dan, a parent: Helen has twice as many dimes as nickles. She has 5 more quarters than nickles. She has $4.75. How many nickles does she have? I know she has 14 dimes, 7 nickles and 12 quarters. How do you put this into an algebra equation? Hi Dan. Use variables (letters) to represent the unknown quantities: d for dimes, n for nickels, and q for quarters. "Helen has twice as many dimes as nickels". So d = 2n. "She has 5 more quarters than nickels". So q = n + 5. "She has$4.75".

So 0.25q + 0.10d + 0.05n = 4.75.

Now you have a system of three equations and three unknowns. Use the substitution method and/or the elimination method for simultaneous equations to reduce it to a single equation involving a single variable. Then solve for that variable and use its value to determine the other two variable quantities.

If you want some examples of using the "substitution method" or the "elimination method", just search for those terms in our Quick Search.

Cheers,
Stephen La Rocque.     Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.