Chapter 1.3, Problem 5P

Mary is labeling tick marks on a number line. Starting at a tick mark labeled 4.90, she labels the next tick marks to the right with 4.91, 4.92, 4.93, …., 4.99. Then she labels the next tick mark to the right of 4.99 with 4.100. Mary then says that 4.100 is greater than 4.99 .

1. Discuss what error Mary is making. Why might Mary make this error?
2. Describe how you might help Mary understand her error and how to correct it.