a little math help, please?

[dougjwray]

This is embarrassing, but I'm turning to you, my bass comrades, for help.
How do you figure out percentages?
For example:
Last year's total = 6,739
This year's total = 3,827
What mathematical operation do you perform to get the percentage reflecting the decline from last year to this year?
(Like, "down 26%")
Thanks in advance.
BTW, the numbers above do not reflect the number of gigs I played annually, NOR the number of basses I purchased.

 

[AaronMB]

Divide?
=.5678

 

[Jackson171]

Change: subtract old value from new value.

Example: You had 5 books, but now have 7. The change is: 7-5 = 2.


Percentage Change: show that as a percent of the old value ... so divide by the old value and make it a percentage:

So the percentage change from 5 to 7 is: 2/5 = 0.4 = 40%

So yours would be 3827/(6739-3827) x 100

 

[etoncrow]

Subtract and divide: (6739-3827)/6739 = 43.2%

example: Sales are down 43.2% from last year

 

[champbassist]

Subtract and divide by the old value because you are attempting to show the decline relative to the base/old value. Like etoncrow did.

 

[dougjwray]

Thanks very much for the quick replies, and that makes perfect sense.

And to show an increase, I assume you would simply do this?

6739/3827 = 1.76, or an increase of 1.76% (or would that be an increase of .76%??)

 

[etoncrow]

Increase: (6739-3827)/3827 = 76.1%

In both examples you are calculating the difference to the base.

 

[Febs]

Thanks very much for the quick replies, and that makes perfect sense.

And to show an increase, I assume you would simply do this?

6739/3827 = 1.76, or an increase of 1.76% (or would that be an increase of .76%??)

Neither. It's an increase of 76%.

The better way to calculate it would be to use the same method as you did for calculating percentage decrease:

If:

Last year = 3827
This year = 6739

Then:

(This year - last year)/last year = (6739-3827)/3827 = 2912/3827 = 76.09%.

 

[i_got_a_mohawk]

6739 is 176% of 3827.

Because you are looking at a rise over the previous year, you can negate the 100% (think of that as the starting point of the comparison), so it would be an increase of 76% (remember to multiply by 100).

 

[dougjwray]

Thanks for your help, everyone. I really appreciate it.

 

[Ocean Man]

The percent change formula I find easiest to remember is:

(new-old)/old.

It gives the % change as a decimal. It's positive if it's an increase, negative if it's a decrease.

 

[Avalon]

Wow!

Staying up late at night posting on TB helped me improve my math silllz.

THANKS TB!