Step by step
The question
Question: find the percent change from 25 to 35.
1 Find the change
First: how much did it change?
It went up from 25 to 35.
35 minus 25 is 10.
It went up, so it is an increase.
2 Compare with the start
Now we compare the change with where we started.
The change, 10, goes on top.
The old number, 25, goes on the bottom.
Careful: we divide by the number we started with, 25.
Not by the new number.
3 Make the bottom 100
Percent means out of 100.
25 times 4 is 100.
So we multiply the top and the bottom by 4.
4/4 is 1.
Times 1 does not change the size.
10 times 4 is 40.
25 times 4 is 100.
40 out of 100 is 40%.
So it is a 40% increase.
4 Check
Let's check: 40% of 25 should be the change, 10.
40% is 40/100.
Of means times.
To keep the numbers small, we divide the top and the bottom by 20.
That is 2/5.
25 divided by 5 is 5.
So it is 2 times 5, that is 10.
And 25 plus 10 is 35, the new number.
So it is right!
Let's look back.
First: find the change.
Then: compare with the start.
Then: make the bottom 100.
Last: check.