Cartoon numbers are used to illustrate how you can change one number into a larger number by adding hundreds, tens and units in a simple process. In the first example, 158 is turned into 258 by adding 100. In the second example, 438 is turned into 679 by first adding a single unit to make 439, then adding 40 to make 479, and finally adding 200 to get 679.
Children could be given a card with an amount of money on it - the digits should all be below five. They could then be provided with a selection of items on a sheet - these items could be related to a class topic. Each item would have a price next to it and children could calculate how much more money would be needed to buy the items using the method shown in the clip. Children could be given two sets of cards, one with numbers smaller than 300, one with numbers greater than 300. They could choose a card from each set, and calculate the difference using the method on the clip. Children could write the numbers on a place value grid with hundreds, tens and ones columns to ensure that they understand the value of each digit.