And just to illustrate that there are always multilple ways to achieve
a result using Excel:

Click cell C1 and, without letting go of the mouse button, drag down to
C5 so that they are all selected (cell C1 is unshaded - it's the
"active" cell)

Input =A1*B1

Press and hold Ctrl, press Enter - Excel will fill the selected cells
with the formula, adusted for the respective cells

Regards

Steve