Hi,

I'm having real problems with the following equation- I'm sure there will be
a way of working this out (possibly even without the use of Excel)...please
help!

Imagine...
x=100 pounds
y = 60% of x
z = 40% of x

I know that if I apply the percentages now, that y = 60 pounds and z = 40
pounds.
However, if I know that y costs twice as much as z, what values am I left
with for y and z?

If I double y I get 120 pounds which is more than the total of 100 pounds!!

Any help gratefully appreciated!

R

"kippers" wrote:
However, if I know that y costs twice as much as z,
what values am I left with for y and z?

z = x/3, and y = 2*x/3. This is simple algebra, to wit ....

x = y + z, and y = 2*z. Subtituting: x = 2*z + z, so x = 3*z, so z = x/3.
Substituting again: y = 2*z, so y = 2*x/3. QED.

However, I assume that "pounds" is currency, since you used the word
"costs". In that case, it would be prudent to ROUND and to compute "y" more
exactly as: y = x - z. In Excel:

A2: =round(A1/3,2)

A3: =round(A1-A2,2)

where A1 is "x", A2 is "y", and A3 is "z". Using ROUND in A3 is optional,
but prudent in order to avoid anomalies of binary computer arithmetic.

Note that "y" and "z" are no longer split simply 60/40%. I don't know if
you purposely changed the rules ("y is twice as much as z"), or if you
misunderstood the split in the first place.

PS: This is my second attempt to post; forgive me if it's redundant. I got
an error when I tried to post the first time, and I did not see my posting
some time later. But the nature of the error does not mean the first posting
failed, and I might have simply not waited long enough to see it. Suffice it
to say, the web interface to MS Discussions Groups is not behaving well at
the moment. "So what else is new?" :-)


----- original posting -----

"kippers" wrote:
Hi,

I'm having real problems with the following equation- I'm sure there will be
a way of working this out (possibly even without the use of Excel)...please
help!

Imagine...
x=100 pounds
y = 60% of x
z = 40% of x

I know that if I apply the percentages now, that y = 60 pounds and z = 40
pounds.
However, if I know that y costs twice as much as z, what values am I left
with for y and z?

If I double y I get 120 pounds which is more than the total of 100 pounds!!

Any help gratefully appreciated!

R