Transcript

INSTRUCTOR:

I'm going to calculate 402 takeaway 238 using the number line. And I've drawn a number line ready for this below. The way I'm going to do this is to actually work out what needs to be added to 238 to make 402.

So I'll start with 238, and I'll end with 402. This is a process known as complementary addition. First of all, I'm going to go to the first tens number after 238-- so that's 240. And to do that, I shall have added 2.

Next I'll work up to the next hundreds number. That's 300. And to make that jump, I should have added 60. And finally, I can get from 300 to 402 in one jump by adding 102. So altogether, I will have added 102, 60, and 2, and that is 164. So 402 take 238 is 164.