Finding the Missing Whole using Bar Models

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!

 

 

 

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