Friday, January 14, 2011

Adding by ten

The other day, we were counting money when i realised N didn't know how to add 10 and 15. He knows how to add 10 to tens i.e.20,40,60, but not with other 2 digits i.e.25,46,78.

Hence, i came up with this activity quite spontaneously. I used my wonderful Montessori counting beads of course!

First, i took out a 10 beads bar and a 5 beads bar. N counted, there are 15 in all.

Then i added another 10 beads bar and asked N '15 + 10 more' equals?

He counted and said 25. I wrote on the doodle board the full equation just so that he can visually see the equation.

I continued with this, by adding another 10 beads bar and asked N how much does 25 plus 10 equals to. We went through this over and over by adding 10 beads to the lot until we hit 105.

I wanted him to see the pattern so i took out another pair this time, in total, 17.

Like the above, we added 10 bar to the beads and calculated all the way up to 107.

Just to make sure he fully understood the pattern, i randomly wrote an equation '64+10=?'. Without the beads this time, i asked N to give me the answer to which he said '74'. I wrote a couple more equations and was satisfied that he has grasp the concept.

We'll keep practising!


  1. If I'm not mistaken, the grey ones are actually subtraction beads? ;D

  2. Ah I purposely chose the grey beads cos I wanted them all in the same color. My other beads are in varying colors. I didn't want N to remember the number if beads by color- which I know he'd. I wanted him to do the hard way by counting then individually.

  3. Oh, apparently the child should simply memorise the colours, but yes, I've seen mine couting them too, so I don't think it's affected him. I was quite fastidious about getting the beads in the "correct" colours though - twas not a easy task!

  4. ha! Ya, i know it was suppose to be colored coded. But im not that anal, im happy as long as i get the point across in the manner that N can understand.


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