Question

$$\begin{array}{ccc}{x}_i& f_i& f_i{x}_i\\ 4& 10& ........\\ 8& 11& ........\\ 12& 9& .........\\ 16& 13& .........\\ & & \sum f_i{x}_i=..........\end{array}$$

Find the value of $\sum f_i{x}_i$.

• A. 40
• B. 88
• C. 444
• D. 208

Answer 1

The correct option is C 444

Here, each term on the rightmost column is the product of the corresponding two terms on the $1^{st}$ two columns. The $1^{st}$ column is class marks' $\left(x_i\right)$ list. And the $2^{nd}$ column is frequencies $\left(f_i\right)$ for these class marks. The $3^{rd}$ column is the product of these two columns i.e., $f_i{x}_i$.

For first row, class mark ($x_i$) = 4, frequency ($f_i$) = 10 and product ($f_i{x}_i)=40$. Similarly, the products of other class marks can also be found.

$\therefore$The sum of these products $(\sum f_i{x}_i)=4\times 10+8\times 11+12\times 9+16\times 13$
$=40+88+108+208=444$