11.1 Using Metal Methods

some percentages are easy to find because they are simple fractions.
There are examples of these on the first page of this unit.

You can use the easy ones to work out more complicated percentages.
You can often do this quite easily. You do not always need a calculator.

If you know 10% you can find any multiple of 10%

WORKED EXAMPLE:

There are 4600 people in stadium. 58% are males. How many is that?

100% = 4600

50% = 50% + 10% - 2% 
These are all easy percetages to find

50% = 2300
50% = 1/2

10% = 460
1/10 is easy. Just devide by 10

1% = 46
Divide 10% by to find 1%

58% = 2300 + 460 - (2 x 46) = 2668  
Do this sum in your head or on paper

Exercise 1:

Work Out:

a) 35% of 84
b) 49% of 230
c) 77% of 4400

Exercise 2:

Work Out:

26% of 78 = 20.28

Use this fact to find:

a) 52% of $78


b) 9.5% of 256

You may check this website if you still didn't understand:

http://www.mathsisfun.com/percentage.html
http://www.homeschoolmath.net/teaching/percent/percent_of_number_mental_math.php

Youtube: