Grass Act

In this Lesson, students estimate the number of blades of grass in a given area. Choose an appropriate section of the school yard or nearby park. For the number of blades of grass to be in the millions, an area greater than 20 sq. yd. is needed. This estimate is based on student-collected data. If a square inch of grass has about 40 blades of grass, then 20 sq. yd. of grass will have about 1,000,000 blades of grass. The number of blades of grass per square inch will vary from lawn to lawn.

Not all schools have access to grass, so four options are outlined below.

You may choose to use one of the three man-made alternatives in this activity: estimating the number of loops on a towel, holes in a screen, or holes in nylon netting. However, the numbers will not be quite as large or the magnitude of the amounts as visually accessible. To actually show a number well into the millions, many feet of towel, screen, or netting are needed.

1. Estimate the number of blades of grass in a given area. If you have a grassy lawn to use as your representative area but are not comfortable with taking students outside, consider bringing a piece of sod into the classroom. The students can do their sampling with the sod and the experience can be nearly as rich. Give students the area of the section of lawn in square yards or square feet; then ask them to estimate the number of blades of grass in the lawn. Alternatively, students can solve one of these problems:
• If the classroom floor were covered with grass, how many blades of grass would there be in the classroom?
• How many blades of grass are in a football field?
2. Estimate the number of holes in nylon netting. Nylon netting is an inexpensive alternative for this activity. Found in most fabric stores, one yard of netting that is 72 inches wide has about 200,000 holes. Five yards of netting provides a good, concrete look at just over 1 million holes.
3. Estimate the number of holes in a screen. Another alternative, though slightly more costly, is window screen. A piece of screen 71/2 feet square will have about 1 million holes. If you use window screen, look for plastic or fiberglass screen instead of metal to prevent accidental cuts.
4. Estimate the number of loops on a towel. A final alternative is a towel. The loops that make up the pile are a little trickier but possible to count. A typical hand towel measuring 15 inches by 20 inches will have about 100,000 loops.

This Lesson is written as if the activity will be completed using grass on a lawn. If you choose to use an alternative activity, adjust your plans accordingly.