How can I move the summation equation that appears at the bottom of column 3 to be centered with the column 3rd column. Using \hspace hasn't been successful thus far.
\begin{tabular}{ccr@{\hspace{1pt}=\hspace{1pt}}r}
$X_j$&$f_j$&\multicolumn{1}{r}{$f_jX_j$}\
\hline
28&1&(1)(28)&28\\
27&0&(0)(27)&0\\
26&1&(1)(26)&26\\
25&2&(2)(25)&50\\
24&3&(3)(24)&72\\
23&4&(4)(23)&92\\
22&3&(3)(22)&66\\
21&0&(0)(21)&0\\
20&1&(1)(20)&20\\
19&2&(2)(19)&38\\
18&1&(1)(18)&18\\
17&0&(0)(17)&0\\
16&1&(1)(16)&16\\
15&0&(0)(15)&0\\
14&1&(1)(14)&14\\
\hline
&$n=20$& \multicolumn{1}{c}{$\displaystyle\sum^{k}_{j=1}f_jX_j=440$}
\end{tabular}
& $n=20$ & $\displaystyle\sum^{k}_{j=1}f_jX_j$ & 440
for the last row seems to be what you need?=
? I hoped there would be a way using\multicolumn