Acoin contains 1.25 grams of nickel and 3.75 grams of copper, for a total weight of 5 grams. what percentage of the metal in the coin is copper?

So,

To find the percentage that the copper comprises, just divide the amount of copper by the total amount of metal in the coin.  In this case, we will change the denominator so that it is 100, which can easily be converted into a percentage, which is really just a fraction out of 100.



75%

75% of the metal in the coin is copper.

Hope this ; )