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What do you notice about the numbers involved?
What might the - sign tell you?
Where did the girl in the video make a slip-up?
What should she have done instead?
Six new homes are being built! They can be detached, semi-detached or terraced houses. How many different combinations of these can you find?
Start with four numbers at the corners of a square and put the total of two corners in the middle of that side. Keep going... Can you estimate what the size of the last four numbers will be?