These tasks are designed to practice mental arithmetic. Add up to a full ten thousand, one hundred thousand or one million.

It is important that you calculate from the ones over the tens etc. always further up to the full ten thousand.  

An example should make this exercise easier for you, if not everything is clear yet.

77 + 23 = 100, then add up to 100.

8764 + ____ = 10 000?

We start with the ones digit: + 6 together with 4 makes 10. But this results in a carry for the tens digit. This means now: 7 + 3 = 10 for the next digit and so on. 

8764 + 1236 = 10 000

As you can see, padding is easier than figuring out the inverse: 

10 000 – 8764 = 1236

The worksheet with these tasks is part of the exercise booklet

Maths lesson 4 - Fit for the next level