Doubling and Halving

In class, we learned a new strategy called Doubling and halving 

When you do this strategy you have to think about how can you make it easier  

5 x 48 = 240

10 x 24 =240

For example: 

I doubled the 5 to become 10 then I halved 48 to become 24 and that's how I got my answer.

6 x 3.5 = 21

3 x 7 =21

For example:

I doubled the 3.5 to become 7 then I halved the 6 to become 3 and that's how I got my answer.