Using doubling and halving. Maths.

WALT use doubling and halving for x.

E.G 

 halving of 18 = 9

doubling of 10 = 20

E.G

4 x 8 = 32 or 2 x 16 = 32

4 x 20 = 80

or

8 x 10=80

5 x 18 = 90

doubling of 5 = 10

halving of 18 = 9

10 x 9 = 90

4 x 18 = 72

doubling of  4 = 8

 halving of 18 = 9

8 x 9 = 72

How do you do your  doubling and halving?