Math question--help needed

[TBH]

I had to take an elementary algebra course in college because I couldn't test out of it, okay, so don't laugh at me.

How do I figure out percentages backwards? I know how to figure out how much, say, ten percent of 36,000 is, for example. You just do 36,000 X .10=3600. No problem.

But if I know something costs x amount, how do I figure out what percentage of my gross income it is? Is there a simple mathematical equation for this?

Here's my question. My mortgage payments are 565/month, or 6780/year. My gross household income is about 60,000. I can easily figure out that our mortgage payment costs us about 10 or 11 percent of our gross, but how do I figure it out exactly?

The only way I can figure to do it is to figure out 1% of my gross income (600) and then divide my total mortgage payment by that number. But there's gotta be a way to be more precise than that.

Thanks.

[DivaJen]

Originally Posted by claire

I had to take an elementary algebra course in college because I couldn't test out of it, okay, so don't laugh at me.

How do I figure out percentages backwards? I know how to figure out how much, say, ten percent of 36,000 is, for example. You just do 36,000 X .10=3600. No problem.

But if I know something costs x amount, how do I figure out what percentage of my gross income it is? Is there a simple mathematical equation for this?

Here's my question. My mortgage payments are 565/month, or 6780/year. My gross household income is about 60,000. I can easily figure out that our mortgage payment costs us about 10 or 11 percent of our gross, but how do I figure it out exactly?

The only way I can figure to do it is to figure out 1% of my gross income (600) and then divide my total mortgage payment by that number. But there's gotta be a way to be more precise than that.

Thanks.

Take the part (6780) and divide it by the whole (60000). The answer you get (.113) will be a decimal - move the decimal point to places to the right (or multiply by 100) and you'll have your percent - 11.3%.

[Haku]

Don't feel bad. It can be confusing, especially if you're tired from work and whatever else is going on in your life. The most important thing is that you're crunching the numbers when everyone else is just blindly paying the minimum without giving it a second thought.

Short Answer:
On a calculator, you would type in your mortgage (per year) then divide that by your gross income (per year).

Therefore, 6780 / 60000 = 0.113 or 11.3%

Long Answer:
If you really want the explanation, let's build on what you know. We know that:

36,000 X .10 = 3600

Like you said, no problem. Because it's an equation, you can manipulate it any way you want so long as you do so with both sides of the equation. In this case, we can divide both sides by 36,000, like this:

36,000 / 36,000 X .10 = 3600 / 36,000

On the left side, 36,000 divide by 36,000 equals 1, and 1 x .10 is still .10. Therefore, the equation can be reduced to the following:

.10 = 3600 / 36,000

Looks about right, eh?

Another way of expressing this is to replace the numbers with what they really are in English, which is:

Percentage = Mortgage per year / Gross income per year

You can flip that too, to make it easier to read:

Mortgage per year / Gross income per year = Percentage

That's basically how I arrived at the short answer. Hope that helps.

[TBH]

Thanks, you guys rock.

Now, time to close the library and go home and collapse. Got up early this AM for a job interview and then worked til 10PM.

No wonder I'm tired! But I'm happy, dammit.

[cbmeeks]

Originally Posted by claire

Thanks, you guys rock.

Now, time to close the library and go home and collapse. Got up early this AM for a job interview and then worked til 10PM.

No wonder I'm tired! But I'm happy, dammit.

Hope your job doesn't require math!

HAHAHA

JUST JOKING!

I had to ask a simple math question too but mine was a "I = P r t" question.

[TBH]

You know, the thing is I'm really good at doing math quickly in my head. It's just that I can never remember formulas and I have a hard time with mathematical concepts. I can easily add, subtract, divide, multiply pretty complicated numbers (I usually figure out the bill when eating in a restaurant with a large group of people) but I just can't ever remember more challenging stuff.

So, yes, thank you, my math skills are totally adequate for my work.

[cbmeeks]

hey, I was just pulling your chain.

the sad truth though, is that most Americans can't do 5th grade math...even on paper. :-(

[TBH]

I think I'm a little touchy about it. I don't like to look like a ditz.

[Ima saver]

The sad thing is, I did well in all advanced math classes (algebra, trig, etc.) but have never used it. I use basic math (business math) the most. (Of course I graduated almost 45 years ago)

[cbmeeks]

touchy? you mean about asking a math question?

hey, I look at it this way. There are lots of people out there that are better than me at math. But can they build an NTSC video circuit using only a SX28 microcontroller? I think not. :-)

So you see, no biggie.

I thought,what is Algebra for, anyway.? But I actually have used it in real life. Who would have thought.

[Ima saver]

cbmeeks, not only could I not built it, I have no idea what you are talking about. I am still living in the last century!!

[markio26]

take the big numbers and divide them into the little numbers is what i was taught......look at divajen's comments.. good info. from all the comments.. if you look in my blog.. i posted the average % for each budget category...hth.
i would tell you that you have too much vehicle debt and cc debt.. i would try to eliminate this debt, even if i had to sell the vehicles. you maybe having good fortune right now, but, life changes dramatically sometimes.. building up retirement and crisis fund is most important..