# Need Help With an Equation

Discussion in 'After Hours Lounge (Off Topic)' started by WillG, Jun 17, 2007.

1. ### WillG Producer

Joined:
Jan 30, 2003
Messages:
6,150
428
Trophy Points:
9,110
This may seem like simple stuff for some of you geniuses here (sincerely) but I have not done this in years. My wife is studying for a financial test with math she has not done in years. And this has got me somewhat stumped as well.

Can someone show me how to solve for x in the following equation

362.81=350.45+350.45(.0525)-350.45x

x=1.7231

2. ### SethH Cinematographer

Joined:
Dec 17, 2003
Messages:
2,867
0
Trophy Points:
0
1. Mulitiply 350.45*0.0525 (=18.398625)
2. Add the result above to 350.45 (=368.848625)
3. Move result to left side of equation by subtracting it over (=-6.038625)
4. Divide result above by -350.45

X = 0.017231 . . .

3. ### Keith Mickunas Cinematographer

Joined:
Dec 15, 1998
Messages:
2,041
0
Trophy Points:
0
This is an odd looking formula, but it's not hard to solve at all. First subtract the two numbers on the right that don't have X from both sides. Then merely divide by -350.45.

4. ### WillG Producer

Joined:
Jan 30, 2003
Messages:
6,150
428
Trophy Points:
9,110

Oh, so I guess that makes me dumb

Just kidding

I figured out what I was doing wrong. I was trying to solve it in Excel. And I typed in, literally (.0525) which Excel treated as a negative number I've had a few beers

Thanks. I can use the refresher

5. ### BrianW Cinematographer

Joined:
Jan 30, 1999
Messages:
2,563
38
Trophy Points:
0
Real Name:
Brian
Another way to look at it is to associate everything on the right side of the equation, which is made possible by every term on the right side having the explicit factor of 350.45 (presumably the beginning balance of an interest-bearing account, or something like that):

362.81 = 350.45 + 350.45(.0525) - 350.45x

362.81 = 350.45(1 + .0525 - x)

362.81 / 350.45 = 1.0525 - x

x = 1.0525 - (362.81 / 350.45)

x = 0.017231

It yields exactly the same answer (and is algebraically equivalent to) the responses above, but I find that thinking of it in this way is helpful because it associates the beginning balance factor (1) with the interest earned (.0525) and the interest deducted (x) together to give you a single number (1 + .0525 + x) to multiply by the beginning balance (350.45) to arrive at the ending balance (362.81). This gives me a simple formula that relates beginning balance with ending balance, which is much easier for me to wrap my brain around.

[Edit: Sorry, Will, you slipped your last one in before I could finish my response. Had I known that beer was involved, I would have tailored my answer accordingly. ]

6. ### Joseph DeMartino Lead Actor

Joined:
Jun 30, 1997
Messages:
8,311
13
Trophy Points:
5,610
Location:
Florida
Real Name:
Joseph DeMartino
7. ### Keith Mickunas Cinematographer

Joined:
Dec 15, 1998
Messages:
2,041
0
Trophy Points:
0
I knew Excel could be set to display numbers in parenthesis when they are negative, but I didn't think it'd interpret them that way, that's not intuitive at all to me, but then I was a math major, I don't do business math much.

8. ### Joseph DeMartino Lead Actor

Joined:
Jun 30, 1997
Messages:
8,311
13
Trophy Points:
5,610
Location:
Florida
Real Name:
Joseph DeMartino
Wait a minnit - this is the HTF and we don't have a beer smiley, like the one seen here?

Regards,

Joe

9. ### BrianW Cinematographer

Joined:
Jan 30, 1999
Messages:
2,563
38
Trophy Points:
0
Real Name:
Brian
:lager:

:ale:

:malt liquor:

:lite beer:

:near beer:

:beerbeerBEER:

10. ### andrew markworthy Producer

Joined:
Sep 30, 1999
Messages:
4,762
12
Trophy Points:
0
:vintage claret:

That doesn't work either.

11. ### BrianW Cinematographer

Joined:
Jan 30, 1999
Messages:
2,563
38
Trophy Points:
0
Real Name:
Brian
Ooooh! Now we're getting fancy!