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## 6th grade (Illustrative Mathematics)

### Unit 3: Lesson 8

Lesson 15: Finding this percent of that

# Percent of a whole number

There are several different ways to solve problems involving percentages, decimals, and fractions. Watch as Sal finds the percentage of a whole number. Created by Sal Khan.

## Want to join the conversation?

• at a scale of 500 percent a measurment is 165mm. what is the actual size?
• The video teaches how to find a percentage of a number, here you're given the percentage and looking for the original number, so you should reverse the operation, and do division.

What is the number when multiplied by 500/100 (that's 500%) gives 165?
? x 500/100 = 165

You can divide 165 by 500/100 to find the answer, or since we're dividing by a fraction, you can just multiply by its reverse, so it becomes likes this:
165 x 100/500 = ?
(165 x 100) / 500 = 16500 / 500
16500 / 500 = 33

The original number should be 33.
• At , how do you turn the improper fraction into a mixed number?
• You can just divide the numerator by the denominator
• I don't understand how Sal turned the fraction into a decimal. How is 4/5 related to 4 divided by 5? (At )
• The slash in between the 4 and the 5 means division. All fractions are division sentences written in a different form. To convert a fraction to a decimal, you divide the numerator by the denominator. For 4/5, you divide 4 by 5 to get 0.8
• These comments are very old!
Not to waste your time reading this, but if i did waste your time I'm so sorry
• then stop doing it
(1 vote)
• The video teaches how to find a percentage of a number, here you're given the percentage and looking for the original number, so you should reverse the operation, and do division.

What is the number when multiplied by 500/100 (that's 500%) gives 165?
? x 500/100 = 165

You can divide 165 by 500/100 to find the answer, or since we're dividing by a fraction, you can just multiply by its reverse, so it becomes likes this:
165 x 100/500 = ?
165 x 100 = 16500
16500 / 500 = 33

The original number should be 33.
It will help you to understand...if you could then hit a like 👍🏻👍🏻
• this is too quick can someone explain it to me?
• So basically 50% of 100 is 50, and 50% of 5 is 2.5, if you get fractions and decimals then this is easy.
Here is a method to make calculating percentages easier.
Graph paper or any paper recommended
Let's say I want to find 80% of 200, then I would write 200 x 80 (over 100)= ?. The two 0s from the 80 over 100 and 200 cancel out each other. 80 * 2= 160, so 160 is 80% of 200.
Hope this helps
• Can you explain it better Sal other then that Khan Academy is awsome
• Multiply the whole number by 100. The resulting answer is its value as a percentage. Another way is to add a decimal point after the whole number such as 4, and then move the decimal two spaces to the right, fill in each of those empty spaces with a zero, and add a percentage symbol = 400%.
• At , how does multiplying 30/100 (or 3/10) by 6 (or 6/1,) equal 30% of 6?
Or 0.3 (or 0.30) by 6 equal 30% of 6?
• Pay attention to the whole video or try the arithmetic course and see if that helps.