Since N can count in tens, i thought it was time to teach him about tens and ones. Frankly, i taught him many times and in different ways but he didn't seem to understand it. Finally, i found the 'formula'.
Montessori ten beads
Montessori Short beads stair
Number cards in blue from 1-9 (DIY)
Number cards in yellow from 10-90 (DIY)
First, i took out the blue number card and asked N to give me the short stair bead that match the number, in this case 3.
Then, i placed the blue card over the yellow card to make a two-digit number, in this case 23. I showed N that 2 ten beads and 3 (short stair) beads make 23. Sometimes i would painstakingly count them one by one to show N that there are i.e. 23 beads altogether. I did this over and over again with the other cards until i was sure he got it right.
On a another note, N indirectly learnt addition just by doing this activity. He understood that for instance 10 and 2 makes 12, 10 and 5 makes 15 etc. So i am hoping with this current activity he would be able to make out that 20 and 3 makes 23 etc. We'll see!