Butterfly Flowers

Problem | Teachers' Notes | Hint | Solution | Printable page |
Stage: 1 Challenge Level: Challenge Level:1

Why do this problem?

This problem addresses a difficulty that many children experience with the numbers from ten to twenty. The "teens" often cause more trouble than other decades up to $100$. English speakers have a particular problem because of the irregularity of the language used. "Fourteen" can so easily be muddled with "forty" so that many children will write "$41$" instead of "$14$".

Possible approach

This problem would fit in well in a lesson on tens and units or on place value. It can also be used to address difficulties that some children have with the numbers from ten to twenty. You could start by discussing how a number, for example, fifteen is made up from $10$ and $5$.

These cards could be used to introduce the problem. They can also be useful as a set of cards for matching activities or for continuing the problem in pairs with one child removing three cards and the other working out which ones are missing. For long-term use the cards should be laminated.

Key questions

What goes with ten to make this number?
What goes with this number (for example, $3$) to make this number (for example, $13$)?

Possible extension

The cards could be used by pairs to make up a game for other children to play.

Possible support

When children are counting together make sure that the "teens" are well differentiated from the "tens", for example, that "sixteen" is well differentiated from "sixty".

Some children respond well to using the counting from Catherine Stern's book "Children Discover Arithmetic". It can be called something like "Funny Counting". The numbers between $9$ and $22$ go, "onety, onety-one, onety-two ..... onety-nine, twoty, twoty-one..." The numbers get quite regular with this counting at 60!


Published September 2002.