
www.VirtualNerd.com
How Do You Use a Proportion to Find a Part of a Whole?
What is 40% of 220?
Summary
- 'x' is a variable that represents the part of 220 that is 40% of the whole
- A percent proportion is the percent of something over 100 equal to the part of something over the whole
- Our percent is 40
- Our part is x, our unknown
- Our whole is 220
- Cross-multiply to solve for x
- Multiply 40•220 to get the left hand side
- Multiply 100•x to get the right hand side
- 88 is 40% of 220

Notes
-
-
- 'x' is a variable that represents the part of 220 that is 40% of the whole
-
- A percent proportion is a special kind of proportion
- It is the percent of something over 100 equal to the part of something over the whole
-
-
- A percent proportion is a special kind of proportion
- It is the percent of something over 100 equal to the part of something over the whole
-
- 40 goes on the top of the first ratio
-
- 100 goes on the bottom of the first ratio
-
- 'x' is a variable that represents the part of 220 that is 40% of the whole
- It goes on the top of the second ratio
-
- 220 goes on the bottom of the second ratio
-
- 'x' is a variable that represents the part of 220 that is 40% of the whole
- We can solve our proportion for x by cross-multiplying
-
- 'x' is a variable that represents the part of 220 that is 40% of the whole
- The means-extremes property of proportions says we can cross-multiply to solve for x
-
- First multiply the extremes, 40•220
- This is the left hand side of our equation
-
- Then multiply the means, 100•x
- 'x' is a variable that represents the part of 220 that is 40% of the whole
- 100x is the right hand side of our equation
-
- Now we have 8800 on the left hand side
- This is equal to 100x
-
- 'x' is a variable that represents the part of 220 that is 40% of the whole
- Division is the opposite of multiplication
- So to undo the multiplication, we need to divide by 100
-
- Dividing 8800 by 100 leaves us with 88 on the left hand side
- The 100's cancel out on the right to leave us with x
- So our variable, x, is equal to 88
- That means 88 is the part of 220 that is 40% of the whole
-