9.1 Estimate Sums and Differences (p.200-203)

I.Use benchmark numbers to estimate:
A. Benchmark numbers are numbers that are easy to work with --> 0, 1/2, 1 whole
B.Compare the numerator (top) to the denominator (bottom)

Find out if the numerator is:

• far away from the denominator (ex. 1/9: between 0 and 1/2, but closer to 0--> 0)


• close to half of the denominator (ex. 3/5: between 1/2 and 1, but closer to 1/2--> 1/2)


• almost the same as the denominator (ex. 7/8: it is between 1/2 and 1, but closer to 1--> 1 whole )

II. Use a range to estimate when you are working with quarters (equivalent to fourths)

A. 1/4 is exactly in the middle between 0 and 1/2 so we can use either 0 or 1/2 as estimates for 1/4.

ex. 3 1/4 + 2 7/8

3 1/4--> could be 3 or 3 1/2 for our estimate - use both to find the range

2 7/8 would become 3 for our estimate

3+3 = 6

3 1/2 + 3 = 6 1/2

The range is between 6 and 6 1/2, our estimate could 6 1/4 which is between 6 and 6 1/2