After students are able to find the percent of a number, they can explore what it means to find the missing whole. We will look at 3 examples of how to teach this with percent bars.
Example 1
6 is 20% of what ? First, we need to break our model into 10% sections. 6 is the 20%, so above 20% put the 6.
Now we have to determine what the whole bar is worth. If 20% is worth 6, then 10% is worth 3. If we continue to count up by 3, we can see that the whole bar is worth 30. Therefore, 6 is 20% of 30.
Example 2
12 is 75% of what? Since this problem is asking for 75%, we can break our model into 25% sections.
12 is the 75% so above 75% we are going to write a 12. If 75% is worth 12, then every 25% is worth 4. if we count up by 4 we see that the whole bar is worth 16.
Example 3
12 is 15% of what? If we use our 10% section model, we can determine that 15% is right between 10% and 20%.
There are 3, 5% sections in 15% so if we divide 12 by 3 we can determine that each 5% section is worth 4. If we continue counting up, we see that the whole bar is worth 80. Therefore, 12 is 15% of 80.
Using percent bar models has been monumental for my students. This visual gives them what they need to understand what it means to find the missing whole. I hope your students find success with this!
Math Hands On 