Rand () causing Problems.

[Guest]

I am having all sorts of problems with my spreadsheet. I fixed some but I
think the problem lies within the Rand() function.
I want a spreadsheet (on one page) (what appears to the students) four
columns of simple arithmetic problems.
I want to be able to adjust the operation: +-*/. And have the spreadsheet
calculate the solutions.
However I also want to be able to set a range of values such as the first
column using numbers 1-10 the second 1-15 third 1-20 and fouth 1-25.
However when I use the random integer function and have the spreadsheet
calculate the solutions it is off on many of the solutions.
In cell A1 I have the function lets say "+".
In cell B2 I have the upper limit for the integers
In cell B3 I have the lower limit for the integers
In cell B4 I have: =RAND()*(B$2-B$3)+B$3
In cell K4 I have=B4 (this is the first number in my problem)
However when I use in cell AH4
=SUMPRODUCT(($A$1="+")*($K4+$M4)+($A$1="-")*($K4-$M4)+($A$1="X")*($B4*$C4)+IF($M4<>"",($A$1="/")*($K4/$M4),0))
The solution varies.
Thanks for your time.

 

[Biff]

Hi!

Hmmm.....

Depending on which operator is entered in A1 and if M4 is either empty or 0,
the results vary, but they are correct.

($B4*$C4)

Is that a typo? All other references are to M4.

Here's another (shorter) way to write your formula:

=IF(OR(M4={"",0}),0,CHOOSE(MATCH(A1,{"+","-","x","/"},0),B4+M4,B4-M4,B4*M4,B4/M4))

Biff