Begin a class discussion about what it means to double or halve numbers. Ask students to give some examples of doubling or halving (e.g. half of 4 is 2; double 10 is 20; and so on). Ask students to share some situations in which they would double or halve numbers (e.g. baking, making groups, etc.).
Bring a group of students up to the front of the room, such as 5 students, and ask them how they would double the size of the group. Each student can pick another student to join the group at the front of the room.
Next, bring a group of an even number of students to the front of the room. Tell them to halve the group. Send half of the group back to their seats.
Distribute the Baby Weight activity sheet to each student.
Discuss the "rule of thumb" as stated on the activity sheet: A baby doubles its weight in six months. Complete the first two rows as a class. Give students time to complete the rest of the chart individually.
Using a red crayon for the birth weights and a brown crayon for the six-month weights, explain how to complete the bar graph. Students should pair up and compare their bar graphs. The teacher can circulate throughout the room to check for accuracy.
You may wish to have students create additional bar graphs for other babies, similar to the ones in questions 2 and 3 on the activity sheet using grid paper.
Solutions to the Baby Weight Activity Sheet
The following are the missing numbers from the chart (question 1):
Amy 10
Benito 8
Cathy 18
Demetrius 16
Erik 14
Fran 6
Greg 5
As a class, discuss the similarities and differences between the two graphs completed (questions 2 and 3 on the activity sheet.) Students may point out that both graphs are bar graphs and show a comparison between birth weight and six-month weight. Students may also say that the graphs show the weights of different babies and the fact that they "look" different (one is horizontal and one is vertical.
