Unit 4 Contents

1. Lee Yah estimated that the three countries with the most satellites have about 12,000
   satellites in orbit altogether. Lee Yah wrote this number sentence showing the convenient numbers she chose:
   12,000 = 3000 + 5000 + 4000
   Explain how Lee Yah arrived at her estimate.
2. Find another estimate for the number of satellites launched by these three countries. Explain your thinking.
9. Estimate the total number of artificial satellites orbiting the earth. Show or tell how you arrived at your estimate.

When Do We Estimate?

While Grace was solving problems about satellites, she asked Mrs. Dewey, “When should I estimate an answer and when should I find it exactly?”

“Good question,” replied Mrs. Dewey. “Let’s think about that with your classmates.”

Mrs. Dewey’s class made a chart to show when it makes sense to estimate.

1. Write a second example for each of these situations.
2. Can you think of another situation when you might want to estimate rather than find an
   exact answer?