(ii) Deductively explain that these rules work:
For 50 + 94:
Going down one number from 50 adds 10.
Going up from 94, on the other hand, subtracts 10.
Therefore, 60 + 84 = (50+10) + (94-10) = 50 + 94.
In the same way, going left subtracts 1 and going right adds 1, so 51 + 93 = (50 + 1) + (94 – 1) = 50 + 94.