Mentally Calculating %

     

Children should always know the relevance of what they are learning in maths to their own lives.

To continue exploring our central idea:

We use fractions, decimals and percentages in a variety of ways in real life situations.

we explored mental strategies we can use when we see percentage discount sales.

We began by discussing places we see % discounts - shops, TV and magazine advertisements etc.

I drew a line on the board from MOST COMMON discount % we see in real life to LEAST COMMON.

This what we thought:

     

When asked why we don't see 12 . 5% discount sale signs, we decided that the maths is too complicated for people to be able to work out mentally and so shops use easier % discounts.  

With this continuum, we began with 20%.  Using the THINK-PAIR-SHARE routine, we thought of the easiest way to mentally calculate the new price discounted in a shop firstly by ourselves, then shared our strategy with a partner and then students were invited to share with the class.

Some mental strategies shared: