not able to understand round up exercise

Rounding up 84,791 to 100,000 we get 15209. This can be written as the following:

84,791 = 100,000 – 15,209

Here are the steps to find the amount you rounded up which is 15,209

The last digit adds up to 10 and all the other digits except the last digit add up to 9.

Keeping this principle in mind we do the following:

First digit 8 in 84,791 adds up with 1 to get 9. So 1 is the first digit of the amount rounded up 15,209.

8 + 1 = 9

Second digit 4 in 84,791 adds up with 5 to get 9.  So 5 is the next digit of the amount rounded up 15,209.

4 + 5 = 9

Third digit 7 in 84,791 adds up with 2 to get 9. So 2 is the next digit of the amount rounded up 15,209.

7 + 2 = 9

Fourth digit 9 in 84,791 adds up with 0 to get 9. So 0 is the next digit of the amount rounded up 15,209.

9 + 0 = 9

The last digit add up to 10 so

Last digit 1 in 84,791 adds up with 9 to get 10. So 9 is the next digit of the amount rounded up 15,209.

1 + 9 = 10

Putting the numbers together we get 15209

I have written the steps for clarity. You should be able to immediately find the amount you rounded up by looking at the number.

Let me know if this clarifies.

Abhishek