The Total column is allowFormula: each row uses a
relative formula (=B1*C1, =B2*C2, and so on), and the
last row totals the column with =ROUND(SUM(D1:D5),2). Double-click a
Qty or Unit Price cell to edit it and watch the totals
recalculate. Double-click a Total cell to author a formula: type = then a function
name for autocomplete, click another cell to insert its reference (Shift-click for an absolute
$A$1), or drag across cells to insert a live range. Press
F4 on a reference to cycle A1 / $A$1 / A$1 / $A1. While editing, the
arrow keys move the text caret. Drag the fill handle to copy a formula down (relative references
shift per row). Toggle Show formulas to reveal the sources.