Answer: The required number of cups of water needed is 5.
Step-by-step explanation: Given that the ratio of glue to water in a paper mache glue recipe is 3 : 1 and we need a total of 20 cups of paper mache.
We are to find the number of cups of water that needed.
Let 3x and 1x represents the number of cups of glue and water in the paper mache glue.
Then, according to the given information, we have
Therefore, the number of cups of water that needed is
Thus, the required number of cups of water needed is 5.