[martelle5386]

What is the formula for percents?

[Wondergirl]

Any number divided by 100 = per cent

50/100 = 50%

200/100 = 200%

1/100 = 1%

.2/100 = .002%

[amazin-amber]

for example: say you have to find out 5% of 60.
To do this divide 60 by 100 = 0.6 ( this is how much 1% is worth)
Then multiply by the percent you are trying to find - 0.6 x 5 = 3
Eg 2) Find 30% of 200 = 200 divided by 100 = 2. 2x30 = 60

[KISS]

Na. This is easier.

X% of Y is Z

X% is X/100
What's after of goes in the denominator
Z goes in the numerator

so you get

X/100 = Z/Y

e.g 10 % of 1000 Z

10/100 = Z/1000; solve for Z

Cross multiply and solve for whatever unknown

[morgaine300]

amazin-amber, that is not really a proper way to solve percentages. A percent is out of 100. Therefore, it's the percent number that should be divided by 100, not the other number. i.e. to get 5% of 60, you need to multiply 60 x .05, not .6 by 5. You'll get the same answer, but people have to learn that percentages mean a number out of 100. That's the 5% part, not the 60 part.

And dividing by 100 is where "moving two decimal places" comes in.

I don't see how cross-multiplying is easier. Once you have your percent as a decimal (the x/100) part, you just multipy by Y. That's keeping it simple.

And none of us knows what percentage formulas the poster needed. There's different things to solve for.

[KISS]

Cross multiplying helps when you have a problem that says: 20 is x% of what?

and the technique I suggested ALWAYS WORKS. Eventually you realize about moving decimal places and that 0.5 turns into 50% when formatted as percents. Just look at cells in Excel. 0.5 formatted as a percent is 50%. 50% is half. 75% is 3/4. Your right, "out of 100", but that concept is foreign to somebody just learning.

Problems such as: You got half the project done. What percent of the project was completed? Should be asked. Mathematics is useless and not interesting unless you have some application.

If I gave you a pencil, ruler, and a piece of paper of arbitrary dimensions, say 4.3 x 4.3 inches and I said cut into 10 equal strips would you use division. Nope.

If 100% is perfect score and that's how papers are graded, but now suppose tests are worth 25 pts and you have 2 tests and the final is worth 50 points and the total points determine your grade. You just saw "weighted average", but the math is easier.
All of those similar concepts need to be taught together.

What if I asked, normalize each score to 100%. What does that mean?

[morgaine300]

Eventually you realize about moving decimal places and that 0.5 turns into 50% when formatted as percents. Just look at cells in Excel. 0.5 formatted as a percent is 50%. 50% is half. 75% is 3/4. Your right, "out of 100", but that concept is foreign to somebody just learning.

Then perhaps it's time someone taught them. People don't generally just "come to realize" things like that. I work with a whole heck of a lot of people who have no clue what a percentage is, and no they didn't figure it out looking at Excel. They don't sit there and study things like that. If they know to enter .5, then they already know how to convert 50% to .5, don't they? If not, they could enter 50% and it'll work and they don't have to do anything.

If I gave you a pencil, ruler, and a piece of paper of arbitrary dimensions, say 4.3 x 4.3 inches and I said cut into 10 equal strips would you use division. Nope.

Personally, yes. :-)

[QUOTE=KeepItSimpleStupid]
If 100% is perfect score and that's how papers are graded, but now suppose tests are worth 25 pts and you have 2 tests and the final is worth 50 points and the total points determine your grade. You just saw "weighted average", but the math is easier.
All of those similar concepts need to be taught together.
{QUOTE]

I've been tutoring math for 13 years. I know more about teaching it than most school teachers do. I get college students who can't do basic math and have no idea how to apply it to anything but one or two specific things they learned. There must be some reason for that.

None of the concepts you just mentioned should be taught together. That's too much at once.

[Gernald]

part over whole by 100
or

(part/whole) x 100 = percent

so if I received 10 points on a 100 point test then 10 is the part, and 100 is the whole or the toal, I multiply it by 100, and that gives the percent 10%... I just failed.

[amazin-amber]

Was trying to make it simple, as everyone's making percentages a much bigger problem than they really are - its not that hard!!

[Gernald]

was trying to make it simple, as everyones making percentages a much bigger problem than they really are - its not that hard!!!

Obviously they're hard for the person who asked the question, otherwise they wouldn't have asked.
Interesting way to find percents, I'll have to remember that next time I use them. I've never seen it done that way.
I don't think anyone was insulting you, just the dude who couldn't even explain them properly himself. :)