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# Finding common percentages

Calculating percentages in your head is a valuable skill. Common percentages like 1%, 10%, 20%, 25%, 50%, and 400% can be easily converted into fractions (e.g., 1% = 1/100, 10% = 1/10). To find the percentage of a number, simply multiply or divide by the corresponding fraction, making mental math quick and efficient. Created by Sal Khan.

## Want to join the conversation?

• do it in my head? I'm okay-smart, but not that smart
• As a long time number sense supporter, I disagree with your statement, you are plenty smart to do a lot of things in your head, you just have not practiced it enough to get good at it.
If you look at each of the original problems, I believe the first two x1% and x10% would be easy for you, just move decimal two or one place to right. 20% = 10*2, so I believe you could double 45 and move decimal twice. For 25%, you could learn to divide 28 by 4 (since 25%=1/4). For 50%, you could divide 128 by 2 (50%=1/2). 400% = 4, so you could multiply 4*8. I am more confident than you that you can in fact you are plenty smart to do it in your head, all you need is a little number sense training.
• me do not get it
• `You are just turning the percentage to a fraction, then simplifying it, then multiplying it by ___/1, and simplifying that.`
For some reason, I wrote this is in the code font.
• The way I laughed out loud when he said 'this is so much fun'
• This is very fun and interesting when you understand it
• this is confusing
• Watch the video again if you have to. After that you can do a problem to yourself.
• I got bored half way through.
• What is 1% of 900 (if 900 was split into 100 pieces how much would each piece be worth?)
what is 10% of 650 ( If 650nwas split into 10 pieces how much would each piece be worth?)
What is 20% of 45 ( If 45 was split into 5 pieces how much would each piece be worth?)
What is 25% of 28 ( if 28 was split into 4 pieces how much would each piece be worth?)
What is 50% of 128 ( if 128 was split into 2 pieces how much would each p[iece be worth?)
What is 400% of 8 ( If you had 100% of 8 you would have 8, so how much would you have if increased that amount by 4 times)

Thats how i think about it, hope that helps. :)