You can see the original article by David Yanofsky on Quartz here.
Formulas discussed: Sum
What most will notice is that the Total in cell B9 is showing $9,000, but adding up the individual holiday items comes to $9,500. Strangely enough, the pie chart (despite being one of those horrendous exploding ones) looks to be correct. At least it wasn’t a 3D exploding pie.
So what happened. Some peoples guesses on Twitter were that B3 was being edited, but it appears in the chart already.
First, Apple couldn’t make charts. Now, Microsoft can’t make spreadsheets: http://t.co/QUIA6UmJ76
— David Yanofsky (@YAN0) November 5, 2013
Best guess is that the first 5 items were put in, then a blank line, then either a Sum() function or =B1+B2+B3+B4+B5. Then someone went and inserted two new lines for the Surf rentals and Other excursions items. But didn’t check to see that the Sum() range had adjusted to include the two new lines, or update the manual sum. Assuming that Sum() was used, the safest way to insert rows that you want included in a Sum() range (or any function’s range for that matter), is to where possible insert them in the middle of the range, not at the end, as the functions may not automatically include them otherwise.
So what’s the lesson? Always check your work! For totals, just highlight the cells and the total will display in the status bar at the bottom of the window. And even better, have someone else check your work. And use Sum() rather than B1+B2…
Of course, on the plus side, when you make a mistake, you can just say that even the people who created the application can’t make it work perfectly. Failure with others seems to be much more comfortable than failure alone.