# If 30 units = 500 and 300 units = 1500 what would say 80 units = ?

• Nov 14th 2008, 11:39 PM
MWptvf
If 30 units = 500 and 300 units = 1500 what would say 80 units = ?
I think I need a graphing calculator of some kind.

I want a calculator or a formla for a spread sheet or just a quick way to work out a math problem.

If 30 units = 500 and 300 units = 1500

From this a line on a graph could be drawn that would then tell me the value of any number of units.

what would say 80 units = ?

Maybe I could have explained this better. I hope it makes sense.

Any ideas anyone?

Thanks

MIke
• Nov 15th 2008, 03:46 AM
Arch_Stanton
Firstly, we need to find the conversion factor (something like between Celcius <=> Fahrenheit relations):
$\displaystyle 300u-30u=1500-500$
$\displaystyle 270u=1000$
$\displaystyle 1u=\frac{100}{27}+X$
increase of $\displaystyle 1u$ is equal to increase of value $\displaystyle \frac{100}{27}$ and it's obvious, that both scales start in different places, so we need to find the constant number, which will be added during conversion:
$\displaystyle 30u=500$
$\displaystyle 30*\frac{100}{27}+X=500 \Rightarrow X=\frac{3500}{9}$
we can treat it as a function: $\displaystyle u(n)=\frac{100}{27}n+\frac{3500}{9}$
and then: $\displaystyle u(80)=\frac{100}{27}*80+\frac{3500}{9}=\frac{18500 }{27}=688,(185)$

Of course I assumed, that the units are linear to values, in reality, they might look different. I mean, that grafically our function is a linear function, which might be any other one as well. I hope you kow what I mean.
• Nov 15th 2008, 04:09 AM
MWptvf
wow....
Well you lost me after the first line :)

Then I picked it up again at "Of course I assumed,"

I thought you would have said here go to this online calculator and put your numbers in and hit the big red button.

I did it in excel by listing the two columns of data and dividing them up. Crude but it did the job.