Chameleon text and number in spreadsheets. Watch out for this trap.
In Excel, a text is sometimes treated as a text and sometimes as a number. This can be quite confusing and can lead to wrong calculations. Users have to be aware of this and ensure that the cells in a summation are numbers. Here is an illustration. A1 and A2 contain numbers 11 and 12. A3 contains a text "13". In an addition where each cell is explicitly added, as in cell B4, "13" is treated as the number 13. But. In a sum formula, as in cell B5, "13" is treated as a text and is not added to the sum. Spreadsheet users have to be very careful that each cell in a summation is a number. Otherwise, the cell "number" will not be added. This chameleon quality applies to some other formulas also.