We will let variable x represent this unknown quantity in our proportion.
Substitute: Now we can substitute these values into our proportion.
The percent is the unknown quantity in this problem. Identify: The phrase 8 is means that 8 is the part.
The phrase what percent tells us that percent is the unknown quantity.
and we found the solution by substituting into a proportion.
Solving Problems With Proportions
But how would we solve this problem: 18 is 40% of what number? Identify: The phrase 18 is means that 18 is the part.
$$a=r\cdot b\Rightarrow Percent=Rate\cdot Base$$ Where the base is the original value and the percentage is the new value.
Example 47% of the students in a class of 34 students has glasses or contacts.
becomes Solve: Cross multiply and we get: 40x = 18(100) or 40x = 1800 Divide both sides by 40 to solve for x and we get: x = 45 Solution: 18 is 40% of 45 Problem 3: What is 20% of 45?
Identify: The phrase what is means represents the part and is the unknown quantity.