# Unknown variables question

• Mar 25th 2010, 12:09 PM
cassiuscoal
Unknown variables question
I have a math query relating to a calculation I'm required to do on a property auction website. Apologies if this is the incorrect forum but my understanding of different types of math is quite lacking!

I have the following equation:

w = 200,000
x = 5% of 200,000
y = 17.5% of x
z = x + y

w + z = a

I now need to reverse this equation.

m = w + z. m is known, w and z are unknown.

Both variables to the right of the = are unknown but the percentages are constant, even so, surely this is impossible?

cassiuscoal
• Mar 25th 2010, 12:37 PM
harish21
Quote:

Originally Posted by cassiuscoal
I have a math query relating to a calculation I'm required to do on a property auction website. Apologies if this is the incorrect forum but my understanding of different types of math is quite lacking!

I have the following equation:

w = 200,000
x = 5% of 200,000
y = 17.5% of x
z = x + y

w + z = a

I now need to reverse this equation.

m = w + z. m is known, w and z are unknown.

Both variables to the right of the = are unknown but the percentages are constant, even so, surely this is impossible?

cassiuscoal

w = 200,000

x = 5% of 200,000 = 10,000

y = 17.5% of x = 17.5% of 10,000 = 1,750

z = x + y = 10,000+1,750= 11,750

w + z = a

so, a = w+z= 200,000+11,750 = 211,750

According to what you have written,

w + z = a

m = w + z

So m = a = 211,750
• Mar 25th 2010, 12:48 PM
cassiuscoal
Sorry, thanks for your attempt harish but I think my original post confused things. Starting from scratch, ignoring the values in my first post; ill try and simplify it:

z + y + x = 200,000

y = 5% of z
x = 17.5% of y
z = ?

What are x y and z based on 200,000?

Cheers,

cassiuscoal
• Mar 25th 2010, 01:47 PM
Quacky
I would recommend writing the percentages as decimals.

$
y=5\%\times z=0.05z
$

$x=17.5\%\times y
= 0.175(0.05z)$
$= 0.00875z$

Can you tidy up and finish? Just substitute those values into the equation in question.
• Mar 25th 2010, 05:49 PM
rtblue
Starting off from where Quacky left us, we have that

$x=0.00875z$

$y=0.05z$

$z=1z$

Now we continue, and add these up:

$0.00875z + 0.05z + z$

$1.05875z=200,000$

$z=188.9$

Since Y= 5% of Z, we have:

$188.9(0.05)=9.445= y$

So 9.445 is Y. Since X= 17.5% of y, we have:

$9.445(0.175)=1.652875= x$

So:

x=1.652875

y=9.445

z=188.9
• Mar 25th 2010, 06:10 PM
Quacky
I had been hoping to let him/her finish for themself to check that he/she at least partially understands...nevermind (Tongueout)