Magnitude Estimates

100,000s

10,000s

1,000s

100s

10s

1s

• A Magnitude Estimate is a very rough estimate that answers the question:

Is the solution in 1s? 10s? 1,000s ? 10,000s?

• How to make a magnitude estimate:

1. Round the numbers to the nearest 1, or 10, or 100, etc.

2. Make the calculation.

3. Determine if the solution is in 1s, 10s, 100, 1,000s, etc.

• For example:

Make a magnitude estimate for 356 * 17:

1. Round the 356 to the nearest 100: 400.

2. Round the 17 to the nearest 10: 20.

3. Multiply the estimates: 400 * 20 = 8,000

4. The solution of 356 * 17 is in the 1,000s.

5. To check, the actual solution is: 6,052

• Another example:

Make a magnitude estimate for 24.8 * .7:

1. Round the 24.8 to the nearest 10: 25

2. Round the .7 to the nearest 1: 1

3. Multiply the estimates: 25 * 1 = 25

4. The solution of 24.8 * .7 is in the 10s.

5. To check, the actual solution is: 17.36