Question Discussion & Solution

SUM function returns the sum of values supplied. These values can be numbers, cell references, ranges, arrays, and constants, in any combination. Here =SUM(Sales) is incorrect if it is not name of any range.

We can select a single range of cells by dragging cursor over the desired cells.

All elements of a worksheet can be protected from accidental modification.
To protect a worksheet in Excel 2007 and higher versions, click the Review tab, click Protect Worksheet (or Protect Sheet), and click OK.
Excel 2003 and Earlier Versions click Tools > Protection, click Protect Sheet, and click OK.

An array formula is a formula that can perform multiple calculations on one or more of the items in an array. We can think of an array as a row of values, a column of values, or a combination of rows and columns of values. Array formulas can return either multiple results or a single result. For example, we can create an array formula in a range of cells and use the array formula to calculate a column or row of subtotals. We can also place an array formula in a single cell and calculate a single amount. An array formula that includes multiple cells is called a multi-cell formula, and an array formula in a single cell is called a single-cell formula.