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## Class 8 (Old)

### Course: Class 8 (Old)>Unit 7

Lesson 1: Percent change word problems

# Percent word problem: penguins

You're given the percent in this example and asked to find the whole number represented by the percent. Created by Sal Khan.

## Want to join the conversation?

• At why didn't sal simplify his work to 3/15?
• Well, actually if you want to get 3 you have to do 0.3*10. But, you will also get 150 by doing 15*10. As Sal said, you can't multiply only one number (or decimal).
Sorry no one answered before; but it's a good question.
• could you just times 15 by 3 then find how much 10 percent (the remaining percent after multiplying 15 by 3, witch will = 90%) of 15 is?
• Seems like you are doing: 30% of 15, which is a different problem to the one in the video.
The problem in the video tells you that 30% of some number = 15
You need to divide by 0.3 not multiply.
Hope this helps.
• At why is 30% of X is same as 30%*x, why are we multiplying instead of adding?
• "of" basically means "*". like 0.5 of 20 is 0.5 * 20 It makes sense in decimals.
• Another problem I got was: "81 is 56% of what?" I got 144.6429... and it kept going on. Can I just keep it at 144.6?

Thanks!
• Same comment as for your other question... see if you have instructions that tell you where to round the answer (what place value).
• how about if you are trying to find the percent not how many penguins live in zoo?
• Construct a different equation to solve for the unknown variable. In the above video you would have something like:
50X = 15
Solve for X gives you 0.3 which = 30%
• Is there an easy way to work out percentage increase and reduction? My mum showed me an exceedingly complicated way and I don't understand it!
• Percentages are just fractions where the bottom part is always `/100`. So `30%` is the fraction `30/100`. If you multiply or divide by a percentage, you're just multiplying or dividing by that fraction.
• is there a way to make this video simpler because it's not really helping me, just making me more confused.
• Another way to think about this is to solve a proportion of `%/100 = is/of`. The more you practice and substitute the values for `%`, `is`, and `of`, then you can solve percents easily.
(1 vote)
• need help ansering this question .The marching band has 100 members .Twelve of them play the flute .What percentage of the band members play the flute ?