Doubling and halving can be a very effective way of working out quite difficult number problems in your head. These two free maths worksheets look at this skill.
Some examples:
To multiply a number by 15, multiply by 10 and add on half the answer.
36 x 15 = 360 + 180 = 540
When multiplying a number ending in 5 we can double this number and halve the other number before multiplying.
Free Y6 maths worksheets: Revise doubling and halving (pg 3)
Free Y6 maths worksheets: Revise doubling and halving (pg 4)