Gallery Problems Exercise

Marbles in a Cup

Work Time

Marbles in a Cup

Chen has some marbles that are all identical.

He puts 12 marbles in a cup. The marbles and the cup together have a mass of 147 grams.

When he puts 15 marbles in the cup, he finds that the marbles and the cup together have a mass of 165 grams.

Let n = the number of marbles in the cup. Let m = the mass of a marble in grams. Let c = the mass of the cup in grams.

  1. Write a formula for w, the mass in grams of the cup and the marbles together, using just the variables but no numbers.
  2. What is the mass of the cup in grams? Show how you got your answer.