Who is the fairest of them all ?

Why do this problem?

This problem is the third of three related problems. The first problem is Mirror, Mirror... , and the second is ...on the Wall . All three problems ask students to consider the effect of combining two transformations, and then challenge them to describe the single transformations that produce the same results.

This problem follows on from the other two but works equally well on its own. It could be used as extension work for students learning to draw enlargements from a centre of enlargement, using fractional scale factors.

Alternatively, this problem/series of problems could provide suitable task(s) for a unit of work on combined transformations. Some knowledge of vector algebra might be useful for students attempting a full proof.

Possible approach

This printable resource may be useful: Who is the Fairest of Them All?. 

As an extension task, all that is needed is to provide the problem as a worksheet to pairs of students who could then make sense of it together. When they have established the combined transformation for one specific example, a teacher intervention may be appropriate, to move the focus to the general case, asking the key questions below.

Key questions

What if the flag was in a different place?

Possible support

Spend time drawing accurate enlargements. In theclass/groupevery enlargement could be drawn on paper with full details written on and signed; then every student could alternate between doing an enlargement and checking one off the pile.

Possible extension

Ask students to summarise their findings in exactly 20 words (!) then ask if there is anything further that might be varied.