A straightforward introduction to finding 10% off multiples of 10p up to a pound. This can be done in two stages:
Firstly: find 10% of the total. As these are all multiples of ten this is straightforward – just divide the amount by 10.
eg 10% of 50p is 5p
Secondly: subtract from the original amount.
50p subtract 5p is 45p.
However, if you have some really nifty mathematicians they might spot that if you multiply the 5(tens) by 9 you get 450p and divide by 10 to get 45p (or simply multiply 5 by 9). This is a case of finding 90% rather than finding 10% and subtracting from 100%. Tricky, eh?