1. Estimating Sums and Differences
Lesson 4-1

2. Benchmark Numbers
A benchmark is a number that is easy to use when you estimate. When estimating the sums and differences of fractions, we use the benchmarks 0, ½, and 1.
(chart on page 171 of book)

3. ½ ½ 3 5 + 11 25 + = Change each fraction to 0, ½, or 1.
Add or subtract. 3 5 + 11 25 + =

4. Example 2 7 4 + 9 15 = 1 +

5. Estimating Mixed Numbers
If you have mixed numbers, then round the fraction part up to 1 or down to 0.
If the fraction is greater than ½, then round up to 1.
If it is less than ½, then round down to 0.

6. Example 15 3 10 1 4 8 10 6 16 =

7. Homework Time