FINDING THE UNKNOWN NUMBER

[sierra spiegel]

Is it possible to find the unknown if I have the following:
C70=18
C69=9
C71=UNKNOWN

(C70-C69)+(C71-C70)=J71
C71-J71=C70

How do I used excel to find the C71 UNKNOWN????? Right now I can put any number as the unknown and it auto-calculate for me, but the answer is not correct. Please help.

thanks

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[sierra spiegel]

Sorry, I forgot to give the answer so you'll know you did it right:

C71= 4

I need the formula in order to do the next question and C71 is unknown.

thanks



sierra spiegel wrote:

FINDING THE UNKNOWN NUMBER
13-Nov-09

Is it possible to find the unknown if I have the following:
C70=18
C69=9
C71=UNKNOWN

(C70-C69)+(C71-C70)=J71
C71-J71=C70

How do I used excel to find the C71 UNKNOWN????? Right now I can put any number as the unknown and it auto-calculate for me, but the answer is not correct. Please help.

thanks

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[Dana DeLouis]

How do I used excel to find the C71

(C70-C69)+(C71-C70)=J71
C71-J71=C70

Hi. If I am not mistaken...
Your second equation above is saying that J71 equals...

J71 = -C70 + C71

Substitute this into your first equation...
(C70 - C69) + (C71 - C70) = -C70 + C71

Your C71 Cancels out!

All you are saying is that:
C69 = C70

Note that your two C70's on the left hand side that cancel out seems
suspicious.

= = = = = =
HTH
Dana DeLouis

 

[Luizvs]

If you have a complex equation, you can use Excel solver to find it for you.
But your equation is an easy one and you could isolate c71
(C70-C69)+(C71-C70)=J71 and C71-J71=C70
so putting together
C71 - [ (C70-C69)+(C71-C70) ] = C70
=> C71 - (C70-C69) - (C71-C70) = C70
=> C71 - C70 + C69 - C71 + C70 = C70
=> C71 + C69 - C71 = C70
=> C69 = C70

Being that, you may have any value in C71 only if c69 = c70. Otherwise, you
have no solution at all.