Ellen is baking bread. It takes 3 hours to rise 1 ball of dough, and then another 2 hours to bake it. If she makes 4 balls of dough one after another and then bakes them one after another when they're done rising, how many hours will it take?
Reason slowly and give your answer.
20
Ellen takes 4 * 3 = 12 hours in total to rise all balls of dough.

It will take 4 * 2 = 8 more hours to bake each one.

It will take her 12 + 8 = 20 hours to make all of the bread.

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Final answer: 20