Understanding percentages

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governor

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The question we have is this. If a wage of $338 was made this week, it was 30% more than last week, how much was it last week? We tried the subtracting 30% from $338 which is $338-$101.40 =236.60. the 101.40 is of course 30% of $338 but how do I find out what 30% percent of last week was... and I don't know last week, the 338-101.40=236.60 was not correct. any help would be greatly appreciated.
 
The question asks for the number that equals 338 after that number is increased by 30%.

Taking 30% of 338 is not correct because 338 is not the number that is being increased by 30%.

You need to take 30% of the unknown number and add that quantity back to the unknown number, to get a total of 338.


Here's a similar example:

A wage this week is $511.75, and that's 15% higher than last week. What's last week's wage?

Let x = last week's wage

Now we may write 15% of last week's wage as 0.15x

x + 0.15x = 511.75


Do you understand how this equation models the question? Can you do the same?
 
I was hoping you would answer, I realise that the last week number is an unknown, but how do I come up with the unknown answer, knowing only this week number and that it was 30% over last weeks number, and that 30% is 30% of last weeks number?
 
By doing what mmm4444bot suggested rather than waiting for someone to tell you the answer!

mmm4444bot said
A wage this week is $511.75, and that's 15% higher than last week. What's last week's wage?

Let x = last week's wage

Now we may write 15% of last week's wage as 0.15x

x + 0.15x = 511.75
Click to expand...


Okay, "let x= last week's wage" If "15% of last week's pay" can be written as "0.15x, how can you write "30% of last week's wage"?

If this week's way, 15% higher than last week's, is x+ 0.15x, what would that be with 30% rather than 15%?
 
governor said:
I was hoping you would answer
Click to expand...

You may be at the wrong site for help. We don't immediately post answers here. You need to show some effort.


I realise that the last week number is an unknown
Click to expand...

What you don't seem to realize is that we cannot possibly realize your unstated realizations. Got that? :wink:



Please read the main points from our posting guidelines. Cheers!
 
Please don't get angry with me, I don't need to know the answer, I already have the answer, what I don't know is how to find it. You tell me x+15%=511, I understand that( I think) what I don't understand is how do I come up with x. Do I start guessing with the 511-15%? well this doesn't give me the right answer for x, the 15% comes from the x and is added to x and not subtracted from 511. so if i made 511 and that was 15% over last week than what was the amount of LAST WEEK? I guess I could just start multiplying 15% to any number and keep on until I find the answer.
So again 338 is 30% more than last week. should I just start multiplying say... 30% + 200= 260 no, 30% + 250= 325 no, but close, 30% + 260 =338 correct. I was hoping that someone could help me find out how to find X of last week by knowing only this week, and I guess you can't, MAYBE it is only by trial and error. Thank you guys for your help.
 
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governor said:
Please don't get angry with me, I don't need to know the answer, I already have the answer, what I don't know is how to find it.

You tell me

x+15%=511,

I understand that( I think) what I don't understand is how do I come up with x.

No he does not tell you that!

He tells you:

x + 0.15 x = 511.75.......or

x + 0.15 * x = 511.75

Now you need to "isolate" x. To do that you need to realize that "x" is a common factor of the left-hand-side(x + 0.15 * x). You need to factorize 'x' out and solve. Like in

A + A * B = C ← A is common factor in A + A * B

A * (1+B) = C ← Factorize 'A' out

A = C/(1+B) ← solve for 'A'


Do I start guessing with the 511-15%? well this doesn't give me the right answer for x, the 15% comes from the x and is added to x and not subtracted from 511. so if i made 511 and that was 15% over last week than what was the amount of LAST WEEK? I guess I could just start multiplying 15% to any number and keep on until I find the answer.
So again 338 is 30% more than last week. should I just start multiplying say... 30% + 200= 260 no, 30% + 250= 325 no, but close, 30% + 260 =338 correct. I was hoping that someone could help me find out how to find X of last week by knowing only this week, and I guess you can't, MAYBE it is only by trial and error. Thank you guys for your help.
Click to expand...

MAYBE it is only by trial and error.

No it is NOT - see notes above in Blue.
 
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I did It

:D I found out how to do this percentage deal! we found that if we made $338 and it was 30% more than last week,what was it last week? We divide 338 by 1.30 and it brings us to 260. So if we have a total and we know that this number is a certain percentage over another amount, divide the starting number by 1.x ( 1.percentage amount) and it comes up with the number we are looking for. Another example is

500=25% over what number? 1.25/500 ( 500 divided by 1.25) = 400
 
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