Question 43·Easy·Percentages
A bookstore display holds 180 books. If 20% of these books are nonfiction, how many nonfiction books are on the display?
For "What is x% of N?" problems, immediately convert the percent to a decimal (divide by 100) or a simple fraction, then multiply by the total. If the percent is a multiple of 10, you can also find 10% of the number quickly (move the decimal one place left) and scale it up (for 20%, double 10%; for 30%, triple 10%, etc.) to save time and reduce calculator use.
Hints
Understand the phrase "20% of 180"
When a problem says "20% of 180," ask yourself: what operation do I use to find a percentage of a number?
Convert the percentage
Rewrite 20% as either a decimal or a simple fraction so it is easier to calculate with 180.
Perform the calculation
Once you have 20% written as a decimal or fraction, multiply it by 180 to get the number of nonfiction books.
Desmos Guide
Use Desmos to compute the percentage
In the expression line, type 0.2*180 or 20/100*180 and press Enter. The value that Desmos outputs is the number of nonfiction books.
Step-by-step Explanation
Translate the percentage into a usable form
"20% of 180" means 20 out of 100 parts of 180.
We can write 20% as a fraction or a decimal:
Set up the calculation for 20% of 180
"20% of 180" means we multiply 180 by (or by ):
- Using a decimal:
- Or using a fraction:
Compute the product
Now do the multiplication.
Using the fraction:
So, there are 36 nonfiction books on the display.