**Middle School Number Sense Lesson 105: Subtracting Two 3-Digit Numbers that Are Reverses of Each Other**

This concept is a special variation of

**SubWhole**. It appeared

**2 times**this year, with a median placement at

**question # 2**.

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**Number Dojo Level: 86**

What you’re looking for in these problems is a subtraction problem of two 3-digit numbers, with the form of:

**abc – cba**

**multiple of 99**.

**How to Solve:**

- Subtract the second number’s hundreds digit from the first number’s hundreds digit (in other words,
**a – c**). - Multiply this result by
**99**(or even easier, by*100 – 1*).

**Example 1: 781 – 187 = ___**

- 7 – 1 =
**6** - 6 x 99 = 6 x (100 – 1) = 600 – 6 =
**594**

**Example 2: 643 – 346 = ___**

- 6 – 3 =
**3** - 3 x 99 = 6 x (100 – 1) = 300 – 3 =
**297**

**Example 3: 513 – 315 = ___**

- 5 – 3 =
**2** - 2 x 99 = 2 x (100 – 1) = 200 – 2 =
**198**

**Example 4: 712 – 217 = ___**

- 7 – 2 =
**5** - 5 x 99 = 5 x (100 – 1) = 500 – 5 =
**495**

**Example 5: 951 – 159 = ___**

- 9 – 1 =
**8** - 8 x 99 = 8 x (100 – 1) = 800 – 8 =
**792**

**Example 6: 427 – 724 = ___**

- 4 – 7 =
**-3** - -3 x 99 = -3 x (100 – 1) = -300 – (-3) =
**-297**

**Here's a free worksheet to help you practice SubRev3Digit:**

subrev3digit.pdf |

**Up Next for Middle School: FindMedian**