**High School Number Sense Lesson 10: Estimating with Addition of Whole Numbers**

In case you missed it, you will want to check out Tuesday's post, which includes lots of information about estimation problems. On high school tests, EstAddSub appeared a whopping 15 times this year, always at question # 10. Question # 10 on the other 6 tests were about this concept, which removes the pesky subtraction component. So in other words, this lesson is a little easier than the last one.

**Number Dojo Level: 32**

As a quick review, begin these questions by assessing which addend has the most digits. Then round that number to the

**leftmost two digits**. Round every other number to that same place value (regardless of the # of digits they have).

**Example 1: 630 + 2016 + 1974**

- Notice that the largest number has 4 digits. Round to the
**nearest hundred**for each number. Think: 600 + 2000 + 2000. - Write down your answer:
**4600**. - The exact answer is
**4620**, so the acceptable (+/- 5%) range would be between**4389 & 4851**. We are well within range.

**Example 2: 53792 + 24389 + 12345**

- Notice that each number has 5 digits. Round each to the
**nearest thousand**. Think: 54000 + 24000 + 12000. - Add these up to get
**90000**; write that down. - The exact answer is
**90526**, so the acceptable (+/- 5%) range would be between**86000 & 95052**. Notice the wide numeric range of correct answers.

**Example 3: 1234 + 567 + 8 + 90**

- Notice that the largest number has 4 digits. Round each to the
**nearest hundred**. Think: 1200 + 600 + 0 + 100. - Add these up to get
**1900**; write it down. - The exact answer is
**1899**, so the acceptable (+/- 5%) range would be between**1805 & 1993**. We estimated almost exactly.

**Example 4: 44444 + 4444 + 444 + 44 + 4**

- Notice that the largest number has 5 digits. Round each to the nearest thousand. Think: 44000 + 4000 + 0 + 0 + 0.
- Add these up to get
**48000**; write it down. - The exact answer is
**49380**, so the acceptable (+/- 5%) range would be between**46911 & 51849**. We are within range, even though we rounded every number down. This example illustrates how safe we are considering only the leftmost 2 digits of the largest number.

**Here's a free worksheet to help you practice EstAddWhole:**

estaddwhole.pdf |

**Up Next for High School: AddMixDiff**