When you were younger, I know you were sent out into the school car park, to count the different colours of cars.
I was, times don't change that much. To be honest I never knew why other than we had to draw a bar chart.
Now we have progressed from bar charts , we can use this type of information in lots of ways.
This a great way to learn about percentages
Let's think about things.
'Per cent' means 'out of 100'
Writing a percentage means writing it as a number out of 100.
The school car park has 100 cars. 26 of these cars are blue.
To write this as a percentage we say 26 out of 100 are blue, therefore 26%.
If there were 43 blue cars in the same car park it would be 43%, 19 blue cars, 19% etc.
Uh Oh.. but what happens if there are not 100 cars (or 100 of anything for that matter)..Let's see
Suppose there were 50 cars and 8 of them were green. What percentage are green?
We know that 8 out of 50 cars are green. It would be far easier if there were 100 cars.
Let's make it 100 cars then.
Multiply 50 by 2 to get 100.
Whatever we do to one part of the question, we have to do exactly the same to the other part.
Multiply 8 by 2 to get 16.
This is easier now... 16 out of 100 cars are green...so that is 16% (if you cancel down 16 out of 100 you get back to 8 out of 50 so you know this is correct)
More examples 6 out of 25 as a percentage would be 25 x 4 = 100 and 6 x 4 = 24 therefore 24%
You many have to cancel the 'out of ' down to 100
So 52 out of 400 You would divide both numbers by 4 to get 13 out of 100 = 13%
Now for the tricky part
The 'out of' may not be that simple to convert. What would you do if you had to write 8 out of 32 as a percentage? Besides cry..
32 obviously does not multiply up to 100. Could it multiply up to 200?
The best way to find out is divide 200 by 32 to see if it goes in equally. What did you get?
A decimal number, not helpful really. Let us try 300 . Another decimal..?
Keep going until it works.. try 400, 500 etc in this case it is 800 !!!! I thought I was never going to get there..
800 divided by 32 = 25. Now multiply 8 by 25 which gives us 200. We now have 200 out of 800.
To turn 800 into 100 divide by 8 and then do the same to the 200.
Did you get 25%?
Look out for an added extra through out the activities