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## 6th grade (Illustrative Mathematics)

### Course: 6th grade (Illustrative Mathematics)>Unit 6

Lesson 8: Lesson 7: Revisit percentages

# Percent word problem: 100 is what percent of 80?

This word problem is expressed simply which can be confusing to some. Take your time and focus on the what is being asked for. Created by Sal Khan and Monterey Institute for Technology and Education.

## Want to join the conversation?

• couldnt you just divide 100/80 and got 1.25?
• Yes 100/80 = 5/4 it is a same thing 1.25
• Help! In one of Sal's videos it says: Kevin has 24 dollars in the bank today. Yesterday, he had 74 dollars in the bank. By what percentage did Kevin's bank account decrease over the past day? (Round your answer to the nearest hundredth of a percent.) The answer is given as:

The bank account decreased by 74−24=50 dollars

50/74≈67.57%

I have no clue why you would divide 50 by 74. Could someone please talk this out for me! Thanks!
• If you want to know how many percents a is of b, you calculate a/b. That's the basic rule with percentage problems. In this problem they want to know how many percents the amount of the decrease (50 dollars) is of the original amount of money (74 dollars). That's why.

I hope this helped you.
• how do you do 20% of 80
• In math, "of" corresponds to "multiplied by". Therefore, just multiply 20% times 80.
• if 35% of 40 days it rains. how many days out of the 40 days did it rain?
• 80 + 25% of 80
• doesn't the .. is/of = %/100 apply here?
and then cross multiply then divide
• Good question!

Yes the problem can be solved that way, leading to

100/80 = x/100
100 * 100 = 80x
10,000 = 80x
125 = x.

Note that, here, x is already expressed as a percent, unlike in the method shown in the video. So the answer is still 125 percent.

Have a blessed, wonderful day!
• hi i would like this to be less hard
• How do you find the GCF of a decimal or fraction?
• at sal said l25% i thought you could not go over 100 in a percent. can you go over 100 in a percent