What number do you need to add to make a total of 100? Probably the best way is to add on to the next whole ten and then count on in tens to 100.

Adding three numbers: stop watches at the ready to see how quickly these can be completed correctly.

Adding several numbers. A useful tip is to look for pairs of numbers that make 10 and do that part of the sum first.

Find the missing numbers to make the total 100.