Primary 2 · Mathematics

P2 fractions

Four equal parts, one shaded: what fraction is unshaded? It is easy to answer a quarter, the shaded part. The counting is right. The question asked about the other three.

Level
P2
Usually taught
Term 3
Covers
2 concepts

What changes at P2

In Primary 2 your child meets fractions as parts of a whole: halves, thirds, quarters and more. They name the fraction of a figure that is shaded or unshaded, and learn its two parts: the denominator is how many equal parts make the whole, and the numerator is how many are being counted.

They also compare simple fractions and add like ones on a strip labelled "1 whole": six eighths and two eighths make 1 whole.

The sentence that costs the mark

The square is divided into 4 equal triangles, and 1 is shaded. What fraction of the square is unshaded?

What the working usually does

unshaded:the shaded 1 of 4=14\frac{1}{4}

Counts the part that stands out, the shaded one.

What the question asked

unshaded:the other 3 of 4=34\frac{3}{4}

Counts the parts the question names, the unshaded ones.

"1 out of 4 equal parts" is counted correctly, and the shaded part is where the eye goes. The question asked about the other three. P2 worksheets ask about the unshaded part at least as often as the shaded one.

4 equal parts, 1 shaded.

The same question, worked properly

  1. Check the parts are equal

    4 equal triangles

    The square is cut into 4 equal parts, so each part is one quarter of it.

  2. Read which parts are asked for

    unshaded: 3 of the 4 parts

    This is the step that fails. The question asks about the unshaded parts, not the shaded one. This is the word that gets read past, because the shaded part is the one the eye goes to.

  3. Say it, then write it

    34\frac{3}{4} unshaded

    "3 out of 4 equal parts are unshaded" is three quarters. As a check, one quarter shaded and three quarters unshaded make 1 whole.

How can you tell it has clicked?

Fold a paper square into 4 equal parts, colour one, and ask what fraction is not coloured.

A child who points at the three white parts before answering has it. A child who answers a quarter straight away has answered the question about the coloured part.

One thing to try tonight

Colour 1 part of a folded napkin and ask what fraction is coloured. Then ask what fraction is not.

Switch between the two questions a few times, in any order. The habit being built is reading which part the question names before counting anything.

What your child will meet in this topic

  • Fractions
  • Fraction of a Shape

Most Singapore schools introduce this in Term 3, though schools do differ by a term either way. If your child’s school runs a different order, you can set it in the schedule on your dashboard.

What it leads to

P3 compares unit fractions: one third is bigger than one quarter, because 3 equal parts of a whole are each bigger than 4.

From P5 a fraction is taken of an amount rather than a shape, and the same reading habit carries over: which part, and of what?

The same topic in other years

It comes back each year and gets harder, so it helps to see what came before and what is coming.

More in Primary 2

Other topics in the same year, so you can see what sits either side of this one.

See how your child is doing on this topic

StudyLah marks each step separately, so you can see whether it was the setup or the arithmetic that cost the mark.

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