Help children to internalise the concepts by drawing the appropriate pictures and then counting the appropriate parts.
Once the basic doubling of numbers is well known proceed to doubling other figures of two numbers.
Start by using numbers where the units number is under 5.
Double the tens number first then the units number
eg 14 doubled is 28
24 doubled is 48
42 doubled is 84
Now try numbers where the units number is 5 or greater.
Which means there will be an extra ‘ten’ to add to the tens side.
Have the child first check if there WILL be an extra ten.
Double 17 Will there be an extra ten? (YES) because 7 = 7 is 14
So one ten for each 17 plus an extra ten will mean three tens and the four from the fourteen
Double 17 = 34
Double 27 = 54
Double 37 = 74
Double 47 = 94
Double numbers where the tens number is more than 5 and show there will be a hundred.
Double 53 =106
Double 63 = 126
Double 73 = 146
Double 83 = 166