While we were counting money, i realised Sonshine boy didn't know how to add in double digits i.e.50 cents plus 20 cents. Hence i came up with this 'lesson'.
Since he has no issues adding in single digits, i first wrote a single digit equation in black color i.e 5 + 2. After Sonshine boy gives me the answer 7, i wrote 7 on the paper. Then i added '0', in purple, on each digit, making the equation to become 50+20. I showed him that the answer 'magically' becomes 70! I showed him a few more equations to make sure that he sees the pattern.
It worked like a charm! With that 5 minutes lesson, Sonshine boy can now add in tens- mentally too. :) WOOT!