Per cent means out of 100. To find a percentage of an amount, split it into equal parts and take some of them.
There are 100 squares. How many of them are shaded?
100% is the whole amount. 43% is 43 out of every 100.
50% is a half and 25% is a quarter.
10% is a tenth: divide by 10.
Build the rest: 35% is 10% + 10% + 10% + 5%.
Split the amount into equal parts you know. For 10%, divide by 10. For 25%, divide by 4. Then take as many parts as you need: 30% is three lots of 10%, so 30% of 60 is 3 × 6 = 18.
Per cent means out of 100. 43% means 43 out of every 100, so a hundred square with 43 squares shaded is 43% shaded. 100% is the whole amount.
Build it from 10% and 5%. Find 10% by dividing by 10, and 5% is half of that. Then add them up: 35% is 10% + 10% + 10% + 5%. For 35% of 80: 8 + 8 + 8 + 4 = 28.
Write it as a fraction and change the bottom to 100. 12 out of 40 is the same as 30 out of 100, so 12 is 30% of 40. If the bottom won't go to 100 easily, divide the top by the bottom and times by 100.