Friday, August 16, 2013

Semantics and Fractions


15 August 2013

In order to solve a math problem, we need to understand the meaning of the problem and the what the is it asking for.

Three general semantic categories of addition and subtraction word problems 
  1. Before and After
  2. Part and Whole Situation
  3. Comparison

Children need to be given a variation of semantics to learn better. This is to provide them with many versions of problems to solve rather than having only one dimension of a problem and when there is a change or twist in a problem, they get stuck.

Variation is important, repetition is pointless.

For the lesson on fractions, we did 2/3 divided by 5.
We came out with 2 methods to solve it.

  1. Drawing a model and divide it into 15 equal parts so that the whole portion is easier to be divided by 5.
  2. To invert 5 into 1/5. This is because if we are sharing a portion of something into 5 people, it means that each person will get 1/5 of the portion.

We also learnt that 2/3 x 1/5 carries a different meaning compared to 1/5 x 2/3 even though both sums gave the same answer.

1/5 x 2/3 – we are interested in 1/5 out of 2/3
2/3 x 1/5 – we are interested in 2/3 of 1/5

Math is all about understanding.

And I agree!


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