We've doing some mental sums lately. I wanted to teach N how to add in 2s, since he knows the 2 timestable but i was too tardy in preparing the learning materials (hence no pictures). So instead, i just gave him a verbal 'lesson' over meals- so it has became mental sums.
I asked N what is '2+2' (this he knows previously) which he promptly answers '4!'. I went on to the next sum '4+2'?. He gave me the 'i don't know look' so i told him to count in 2s and asked him what number is after 4? He said '6!' so i repeated the question and said '4+2 is equals to 6'. He caught on and was able to answer the subsequent sums, we went up all the way to 22 or more (cannot remember).
After some practice over a few days and explaining to him how to skip count in 2, he spotted the pattern. So i tested him by randomly picking a few sums we hadn't attempted, something like '56+2 or 104+2'. It was amusing seeing him count in his head and his face light up when he got the answers. Because he understood the concept of skip counting in 2s, he can also now add by 2s with odd numbers mentally.
I have to repeat here that i never intended for N to learn sums this early. In fact, i thought he would be ready only by 4 or 5 years old. THe only reason why we've come this far is because he has been showing very strong interest in this area. I feel it will be unfair to him if i insist on slowing down the pace. Also, if i remain at a slower pace, he might get bored and loose interest in learning. My purpose is to spur on his interest and love for learning. And it's been nothing but fun (yes Maths can be quite enjoyable) so far!