Rizul N. answered • 12/21/12

UNC-CH Grad For Math and Science Tutor

**Step 1: Setup**

(Line up your numbers so that the "hundreds" place are top and bottom to each other (like 5 and 7) and the "ones" place are top and bottom to each other (like 3 and 5). Also have the bigger number overall (9513) be on the top. This way you are removing a smaller number (4715) from a larger number and not the other way around if you switch up the setup with the bottom number being on the top and the top number being on the bottom.

9513

- 4715

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**Step 2: **

Start subtraction from right to left (if you are facing the screen; like this direction <-----). Start with the ones first.

Note that 3 is smaller than 5. You can't do that. You have to add a **1 **in front of 3 to make it **13. **Now normally, you would take 1 away from the number adjacent to **13 **on its left side. In this case it is **1 **but note that if we were to take away 1 from **1, **then that number would be **0**. Note the number below that **0 **is 1 and you know that again you have the top number **0** be less than the bottom number **1. **So we cannot subtract 1 from **1. **Instead, like **3, **we put 1 in front of **1 **and make it **11** and then we can subtract 1 from **11 **and the resultant **10 **is greater than the bottom number **1**.** **Then, we have to subtract 1 from **5 **because we put 1 in front of **1 **and made it **11** but again that would result in **4 **which is less than the bottom number **7. **So instead we make that **5 **into **15** and now we can subtract 1 from **15.**** **Now we subtract 1 from **9 **because we converted **5** into **15 **and this results in **8 **which is greater than the bottom number **4**. We can do this. We don't have to put 1 in front of 9 because it doesn't need it. Here is how the setup now looks:

**8** **14** **10**

9 **1**5 **1**1 **1**3

- 4 7 1 5

_______________

4 7 9 8

And here is your answer.

Bill F.

WOW! Very thorough! Maybe more than Byah can grasp(?). Very complete!

12/21/12