How old?

Problem

There is a family with four children. Between each child there is an age difference of 2 years. The oldest child, Maryanne is less than 11 years old. The youngest child, Tom, is older than 5. In between Maryanne and Tom are the twins – Claudia and Cassie. What is the age of each child in this family?

Teaching Sequence

1. Display the 4 pictures – ask the students to make statements that could be true using the pictures.
2. Ask the students to make statements about the pictures using the >, < symbols.
3. Read the problem to the class.
4. Discuss the words older, younger and twins.
5. Brainstorm for ways to solve the problem.
6. As the students work on the problem, ask them to explain their thinking using the <, > symbols. (unless you sepcfically ask the students to use the symbols we believe its liley that they won't use them in the solution). Ask them to explain how they know which symbol to use.
7. Encourage the students to use the symbols in their record of the solution.
8. Share the solutions.

Solution

If the oldest child is less than 11 and the youngest child is more than 5, the ages of the children will be between 5 and 11. So write all the numbers between 5 and 11, that is 6, 7, 8, 9, 10.
As there is a difference of 2 years between each year of birth, the ages must be 6, 8 and 10.
So Maryanne’s age = 10 (check 10 < 11); and Tom’s age = 6 (check 6 > 5); and Claudia’s age = 8 (check 10 – 2 = 8 and/or 6 + 2 = 8); and Cassie’s age = 8 (check 8 = 8).