Question

A coin contains 1.25grams of nickel and 3.75 grams of copper, for a total weight of 555 grams.
What percentage of the metal in the coin is copper?

Answer 1

You should post math-related questions in the Mathematics section.

If there is 3.75 grams copper for every 1.25 grams nickel, then we have 3.75 grams copper for every 3.75+1.25=5 grams of metal.  As a result, 3.75/5=3/4 of the coin is copper.  This is equal to 75 percent.