Finding the Missing Percent
Finding the missing percent means setting up and solving a percent equation when the percent itself is unknown. Using the key translation: Wp × “of” = “is,” you can write an equation like Wp × 80 = 20, then solve by dividing both sides by 80 to get Wp = 0.25 = 25%. This approach works for any percent problem where the percent is what you need to find. It is covered in Saxon Math, Course 2 as part of 7th grade math, connecting to proportional reasoning and real-world applications like calculating what percent a score is of the total.
Key Concepts
Property To find a missing percent, translate the problem into an equation: $$ W p \times \text{of} = \text{is} $$, where $$W p$$ represents 'What percent'.
Examples What percent of 80 is 20? $$ W p \times 80 = 20 \rightarrow W p = \frac{20}{80} = \frac{1}{4} = 25\% $$ What percent of 5.00 dollars is 0.40 dollars? $$ W p \times 5 = 0.40 \rightarrow W p = \frac{0.40}{5} = 0.08 = 8\% $$ Seventy is what percent of 50? $$ 70 = W p \times 50 \rightarrow W p = \frac{70}{50} = 1.4 = 140\% $$.
Explanation Think of yourself as a math detective cracking a code! Convert the word problem directly into a math equation. The number after 'of' is what you multiply by, and the number after 'is' is the result. Solve for the missing variable ($$W p$$), then multiply your decimal or fraction answer by 100 to officially turn it into a percent.
Common Questions
How do you find a missing percent?
Set up the equation Wp × (whole) = (part), then solve by dividing both sides by the whole. For example, Wp × 40 = 10 gives Wp = 10 ÷ 40 = 0.25 = 25%.
What percent of 50 is 15?
Set up: Wp × 50 = 15. Solve: Wp = 15 ÷ 50 = 0.30 = 30%.
What does Wp stand for in percent equations?
Wp stands for ‘what percent’ and represents the unknown percent (as a decimal or fraction) in a percent equation. After solving, multiply by 100 to convert to a percentage.
How do you convert a decimal to a percent?
Multiply the decimal by 100. For example, 0.45 = 45%, and 0.075 = 7.5%.
How does finding the missing percent relate to proportions?
Finding the missing percent is equivalent to solving the proportion part/whole = percent/100. Both methods give the same answer.
When do students learn to find the missing percent?
Finding the missing percent is covered in 7th grade math as part of a unit on percent equations and proportional reasoning.
Which textbook covers finding the missing percent?
Saxon Math, Course 2 covers finding the missing percent using equations.