**High School Number Sense Lesson 89: Multiplying by 5**

Today's lesson is one of the simplest concepts to learn in number sense. It appeared

**5 times**this year on high school tests, with a median placement at

**question # 3**.

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**Number Dojo Level: 5**

I use the

**Double/Half**method to solve these problems. So instead of multiplying by 5, we:

**Divide by 2**- Multiply by 10 (
**add a 0**or move the decimal once to the right).

I will show you a few different varieties that show up occasionally.

**Example 1: 26 x 5 = ___**

- Divide by 2: 26 ÷ 2 =
**13** - Add a 0:
**130**

**Example 2: 116 x 5 = ___**

- Divide by 2: 116 ÷ 2 =
**58** - Add a 0:
**580**

**Example 3: 215 x 5 = ___**

- Divide by 2: 215 ÷ 2 =
**107.5** - Move the decimal once to the right:
**1075**

**Example 4: 3.14 x 5 = ___ decimal**

- Divide by 2: 3.14 ÷ 2 =
**1.57** - Move the decimal once to the right:
**15.7**

Example 5: 10.2 x 5 = ___

Example 5: 10.2 x 5 = ___

- Divide by 2: 10.2 ÷ 2 =
**5.1** - Move the decimal once to the right:
**51**

**Example 6: 13.6 x 0.5 = ___**

- Notice we're multiplying by
**0.5**(dividing by 2) instead of by**5** - Divide by 2: 13.6 ÷ 2 =
**6.8**; we're done.

**Here's a free worksheet to help you practice Mult5:**

mult5.pdf |

**Up Next for High School: CompareFrac**