## Tuesday, March 1, 2011

### Subtraction by 2, 3 & 4

Yes, i have finally decided to move on to Subtraction. It seems to be the natural progression since sonshine boy has grasp the addition concept. He can add in 2s,3s,4s,5s mentally. When i say that i mean that he can add these single digits to any number i.e.4+3, 87+3, 289+5 etc.

Our first subtraction lesson was...over a meal. Yes, i tend to do this kind of impromptu thing. Anyway, i used my fingers once again. Sonshine boy can subtract by 1, so i began my lesson with subtraction by 2.

I started with the equation '10-2' and held up 2 fingers. I told him to count down and we got the answer '8'. I went on with the subsequent equations '8-2, 6-2...2-2'. By then he seems to have gotten the hang of it, so i whacked one new equation for him. I asked him what was '20-2'? This time without fingers, he calculated in his head and gave me the correct answer. After correctly answering a few more equations, i was convinced that he understood it. And the lesson was over in 10 minutes.

Later, i realised he was also able to mentally subtract by 3 and 4 from any numbers (i.e. 57-3, 109-4) - even though i didn't show him how. I reckon this means that he has fully understood the concept of subtraction and how to calculate mentally.

I think this is possible because the boy is particularly interested in maths. Also, i think the right methodology was used such that he could understand. I am really glad that i took time to figure out the right formula for him. It made it really easy for him (to understand) and for me (i don't have to go through every single equation with him). Best of all, he learnt to solve subtractions by 2,3 & 4 (i suspect even 5-haven't tested it yet) even though the 'lesson' was conducted just over 10minutes! WOOT!

#### 1 comment:

1. Wow, I seriously think that you are a genius in teaching maths! I find it's rather easy and most important the kids got to understand it well! Thank you for sharing!