10×10 grids are a great tool when introducing percents because they provide a visual for fractions that are out of 100. Before starting the lesson, discuss with students that the word percent means, “out of 100.” As soon as we have a number out of 100, we have a percent. Percents are a useful tool for comparing because they make every number out of the same thing, 100. It is much easier to compare 80% and 90% than to compare 4/5 and 9/10.
Have students represent 3/100 by coloring in 3 squares out of 100. “What percent is this?” Since 3 are shaded in out of 100, this is 3%.
Have students represent 3/10. Discuss how the fraction means 3 out of 10, therefore we need to start by breaking our whole into 10 equal groups. Students may do this differently and that is fine, as long as they have 10 equal groups.
Once students have 10 equal groups, have them shade in 3 of the 10. Then ask, “what percent is this?” Since percent is out of 100, we have to think, how many are shaded in out of 100, or how many of the tiny squares are shaded in. Students should see that 30 out of 100 are shaded and therefore 3/10 = 30/100 or 30%.
Have students represent 3/4. We need to start by breaking the whole into 4 equal groups. Again, students may break the whole into fourths differently which is fine, as long as there are 4 equal groups.
Then have students shade in 3 of the 4 groups. Ask, “what percent is this?” Since there are 75 shaded out of 100, 3/4 = 75/100 = 75%.
Have students try several examples like this until they have a strong understanding of how fractions and percents relate. It is so important that students get a visual when making sense of fractions and percents.