Mental calculations

Can you use the clues to complete these 6 by 6 Mathematical Sudokus?

Can you use the clues to complete these 5 by 5 Mathematical Sudokus?

Can you use the clues to complete these 4 by 4 Mathematical Sudokus?

Can you use the clues to complete these 3 by 3 Mathematical Sudokus?

Complete the Mathdoku grid using the clues. Can you convince us that the number you have chosen for each square has to be correct?

Do you agree with Badger's statements? Is Badger's reasoning 'watertight'? Why or why not?

Can you match pairs of cards which show the same amount?

Order these four calculations from easiest to hardest. How did you decide?

Can you spot the mistake in this video? How would you work out the answer to this calculation?

Can you put these four calculations into order of difficulty? How did you decide?