Calculating percentages where the denominator is not 100.
Percentages (multiples of 10) of numbers - calculate 10% then scale up
eg
What is 40% of 30
10% 0f 30 = 3 so
40% of 30 = 4 lots of 10% = 12
40% of 30 = 12
simple problem solving using percentages
Calculating percent present or4 percent absent by extrapolation
NHM6 Pp 63, 64