# How Tall Are We?

## Learning Objectives

Students will be able to measure the heights of their classmates using a non-standard method (building blocks instead of rulers). They will also be able to record their data in an organized fashion.

## Introduction/Motivation

By the time they are in kindergarten, most children are well aware of the size differences, most notably in height, between babies, young children, older children, and adults. Furthermore, adults frequently comment on how much children have grown, and from the tone of voice used, children understand that this is a good thing. These comments make a good way to open this lesson.

Gather the class together and ask if grownups ever tell them how big they are getting or how much they've grown since the last time the grownups saw them. Allow a few minutes for children to share their stories. Then ask your students if they have ever had their heights measured at a doctor's office. Ask them to describe how they were measured. You can also ask why they think it is important to have their heights measured. (Growth is an indication of a healthy body; if a child isn't growing as quickly as expected, it can be a sign of an underlying health problem that needs to be treated.)

Finally, explain to the class that you don't have the same equipment that is in doctors' offices. Instead, they can determine their heights in a different way, by measuring each other with building blocks.

## Lesson Background & Concepts for Teachers

### Body of Lesson:

With the class still gathered together, ask one student to come to the front and stand against the wall. Then place a block on end next to the student. Ask if the student is taller than the block. Then ask how many blocks tall they think the student is, i.e., how many blocks will need to be stacked up to reach the top of the child's head. Allow them to share their guesses. It would be a good idea to record their guesses on chart paper or the chalkboard.

Then ask another student to come help you measure the first student. Ask this helper to hold a finger at the top of the block. Then show how you can pick up the block, and move it to a position right on top of where the block was originally. At this point, count aloud and say something like, "One, two, it takes two blocks to go part way up Suzy's leg." Ask a third student to make two tally marks on the chart paper or chalkboard, to show how you can help keep track of how many blocks tall the first student is.

With your helpers, continue to use the block to measure the first student. Ask the rest of the class to help the tally-marking student keep count. When you get to the first student's head, it is unlikely that the student will be exactly as tall as a whole number of blocks. Then you will need to show the class how to decide if the student's actual height is closer to the height obtained by adding a half-block, or if it is closer to that gotten by adding a whole block. Once the determination has been made, ask the class to help you count the tally marks, and then write down the final measurement. Compare this to the guesses students made earlier.

Students might have trouble with the last part of the actual measuring, in which a half-block or whole-block decision must be made. Therefore, it would be a good idea to repeat the demonstration using a new student to be measured and two new helpers.

Next divide the class up into groups of three, and provide each student with a data sheet. The data sheet should be divided into three sections. Each section is identical and contains a space for recording the tally marks and a space for recording the final height measurement (see sample provided). Students should use the three different sections to record the names and data for each of the three students in the group. Make sure everyone understands what needs to be written on the data sheet. Then, provide each group with a measuring block and have the group members work together to measure and record the heights of all three students in the group.

### Lesson Closure

Gather the class together and hold a brief discussion of what just took place. Ask if there was anything particularly difficult about making the measurements, for example. If you noticed any problems students were having you can bring these up and ask how students solved them.

Next, ask each child what his or her height was, and make a list on the chart paper or chalk board. Then ask the class to tell you which student is the tallest, and which is the shortest, based on the numbers listed. Finally, have all the students stand up and ask them to arrange themselves in order by height. Give them time to sort this out for themselves; try to avoid intervening. When they are finished ask them if the data they recorded matches their line-up. In other words, are the students at each end of the line the same students that were measured to be the tallest and shortest? If there are any discrepancies, discuss how these may have come about. These are most likely to occur due to differences in the ways students decide whether the last block added is closer to a whole block, half block, or no additional block. In other words, they are due to differences in the ways students "round" their measurements. This is a fairly sophisticated concept, however, which is likely beyond the grasp of most kindergartners. Therefore, it is fine to mention it, but do not imply that students made poor measurements or got wrong answers if their line-up does not match the recorded measurements. Instead, simply point out that it can be hard to make these sorts of judgments sometimes.

Adapted from Teach Engineering