Hand out example sheets or put pictures up on the wall showing a grid of 100 squares. Ask the class to shade in 25 squares, then explain to the students that 25 percent of the squares are now colored in. Do the same for 50 percent and 75 percent. Explain that "per cent" means "out of every 100."
Demonstrate how to calculate a percentage using math. To work out a percentage, you divide the smaller number by the larger number and multiply your answer by 100. So 25 squares shaded is 25 percent because 25/100 equals 0.25. And 0.25 x 100 equals 25.
Use other numbers to demonstrate percentage calculations. Ask the class what percentage two is of 10, for example. Two divided by 10 equals 0.2. And 0.2 x 100 equals 20. So the answer is 20 percent. Gradually make the numbers more complicated.
Reverse the formula and demonstrate how to work out a percentage of something; 50 percent of 20, for example. Here you divide 20 by 100 to get 0.2, which is one percent of 20. Then 0.2 x 50 equals 10. So 10 is 50 percent of 20.
Show the class some real-life examples of percentages to put the math in context. Cut out stories from the newspaper or advertisements that contain percentages. Get the class to do the calculations based on the percentage a number has gone up or down.