We use round and adjust to help us solve a problem quicker. It allows us to work with numbers that we find easier and more manageable.
Just like with the addition, we have previously used this method when subtracting 9 or a number with a 9 in the ones. This time we had a go at subtracting 8 or a number with 8 in the ones.
1. Round the number to the nearest 10 and subtract it from the first number. (Always remembering to move from right to left on the number line when subtracting, because the value of our numbers are decreasing)
2. Then adjust. Add the amount you took away from the original number, when you rounded the number to the nearest 10. Because we are adding when we adjust, we must jump on to the right on our number line as the value of the number is getting larger!
Have a look at the guide to explain and model this further: