Division is really nothing more than fancy subtraction. For
example, 10 divided by 2 is the same as starting with 10 and continuously
subtracting 2 as many times as needed to get to zero. In this case, you would
need to continuously subtract 2 five times.
- 10-2 = 8
- 8-2 = 6
- 6-2 = 4
- 4-2 = 2
- 2-2 = 0
So, 10/2 = 5.
Now if you tried to do this with 10 divided by 0, you would
never get anywhere, because 10-0 is 10 all day long. You’d be sitting there
subtracting 0 until your calculator dies.
- 10-0 = 10
- 10-0 = 10
- 10-0 = 10
- 10-0 = 10
- …..Infinity
Mathematicians call the result you get when
dividing any number by zero “undefined.” Software like Excel simply gives you an
error when you try to divide by zero. In Excel, when you divide a number by
zero, you get the #DIV/0! error.
You can avoid this by telling Excel to skip the calculation
if your denominator is a zero. Figure 2-9
illustrates how to do this by wrapping the division operation in Excel’s IF
function.
=IF(C4=0, 0, D4/C4)
 |
| Figure 2-9: Using the IF function to avoid a division-by-zero error |
How it works
The IF function requires three arguments: the condition;
what to do if the condition is true; and what to do if the condition is
false.
The condition argument in this example is the budget in C4
is equal to zero (C4=0). Condition arguments must be structured to return TRUE
or FALSE, and that usually means that there is a comparison operation (like an
equal sign or greater-than sign).
If the condition argument returns TRUE, the second argument
of the IF function is returned to the cell. The second argument is 0, meaning
that you simply want a zero displayed if the budget number in cell C4 is a
zero.
IF the condition argument is not zero, the third argument
takes effect. In the third argument, you tell Excel to perform the division
calculation (D4/C4).
So this formula basically says that if C4 equals 0, then
return a 0, or else return the result of D4/C4.
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