# What do the three groups of girls represent?

There are three groups of girls.

• The first group (three girls) has naturally straight hair.

• The second group (four girls) used a curler, some missed a few strands that remains straight.

• The third group (three girls) has naturally curly hair.

You look at them regularly. What do the three groups of girls represent?

I think these are

the digits 0-9.

The first group

consists of digits 147, made out of straight lines.

The second group

consists of digits 2359, made out of some straight lines and some curves. (There are different ways of forming the digits, and some ways of writing 3 and 9 are all-curves.)

The third group

consists of digits 068, made out of curves only. (Some ways of writing 6 are a mixture of curves and straight lines.)

I am a little uneasy

about the asymmetry between 6 and 9 here, though I think it's fairly common to handwrite a 9 as a circle with a vertical line descending from it, and much less common to do an equivalent thing with 6. There's some ambiguity about 3, too.