Word Problems for Young Adults - Book 4

Climate March 1085 - Sign, Wikimedia Commons, Edward Kimmel, released under a Creative Commons Attribution-Share Alike 2.0 Generic license

By Clarence Thompson

This post concludes our preview of word problems from our upcoming Book 4 of the Elementary School Math for a Flying University series.  It consists of two warm-up problems of the kind that kids normally encounter in the ordinary life of kids - plus one problem of the kind that young adults will have to solve when those adults and their families are people of color and they live in a country run by evil people, as is true in much of the United States right now.  The last problem shows how smart people can find ways to solve problems created by the evil people who now run things. 

Warm-Up Problems (by my friend Craig Haynes)

• Nathan grew tomatoes during the summer. He decided to give some to his neighbors and keep some for his family. Nathan grew 1024 tomatoes and gave 477 to his neighbors. How many tomatoes did he keep for his family?

• On the first day of school Lamarra’s teacher purchased 4 pizzas to share among the class. Each pizza has 13 slices. If Lamarra’s teacher ate 4 slices and shared the remainder amongst the 24 students in the class, how many slices did each student get?

A Problem for Young Adults

In the state of Michigan, there is a city named Flint. Six years ago, the Republican governor of Michigan forced the Flint city government to stop delivering clean water to all of its poorest people. Nowadays in Flint, only rich people have access to clean water. And getting clean water to your house is expensive if you live in Flint. Everyone else gets polluted water from the Flint River. (The word polluted means “dirty.”)

On a certain day in Flint, some of the poor residents get together to figure out how they can get clean water to their houses without relying on the City water system. They read a book that says that people need at least 20 liters of clean water each day. (This is not just for drinking, but for things like washing and cooking as well.) The book also tells them how poor people can make devices to filter their own water. In their group they have several houses, and in each house there are 4 people. They decide to build biosand filters system to provide water for each household in their group.  The filters described in the book can provide between 24 and 72 liters of filtered water per day.  However, the more water they provide, the less filtered the water is. Please answer the following questions:

• Say that each filter provides 45 liters per day. How many filters does each household of 4 people need to provide its daily water supply?

• Say that a house of 4 people has built the number of filters which you found in the first part of the problem.  If a fifth person moves into the house and the house members do not build more filters, how much less water do the other members of the house get each day if the water is divided equally?  

• Now suppose that the people in the neighborhood find out that in addition to dirt and germs, the water provided by the City also contains arsenic. The people in the neighborhood know that arsenic poisons people, so they decide to turn their biosand filters into Kanchan© filters by adding rusty nails to the top layer of the filter. This slows down the maximum filtering rate to 36 liters per day. How many filters does each household need in order to meet its daily clean water needs?

• How many biosand filters does a family of 4 persons need if the filters run at their maximum filtering rate? If the family has to convert these filters to Kanchan filters, how much less water will they have every day if they run the Kanchan filters at their maximum filtering rate (assuming that the number of filters stays the same)? If the water is shared equally, how much water will each person in the family get after the biosand filters are converted to Kanchan filters?