$\Sigma(x_{i} - \bar{x}) = \ldots \ldots \ldots$

Rachana had an average score of $45$ from $6$ tests. Her teacher dropped her lowest score,which is $30$,and calculated the average of the remaining scores to decide her grade. Which of the following gives her new average score?

For a given frequency distribution,$A = 450, c = 100, \Sigma f_{i} u_{i} = -20$ and $\Sigma f_{i} = 20$. Then,the mean $\bar{x} = \ldots$

The mileage $(km/l)$ of $50$ cars of the same model was tested by a manufacturer and details are tabulated as given below:

Mileage $(km/l)$	$10-12$	$12-14$	$14-16$	$16-18$
Number of cars	$7$	$12$	$18$	$13$

Find the mean mileage.
The manufacturer claimed that the mileage of the model was $16 \, km/l$. Do you agree with this claim?

The mean of the following frequency distribution is $18$. Find the missing frequency $f$.

Class	$11-13$	$13-15$	$15-17$	$17-19$	$19-21$	$21-23$	$23-25$
Frequency	$3$	$6$	$9$	$13$	$f$	$5$	$4$

Find the mean of the following frequency distribution:

Class	$10-20$	$20-30$	$30-40$	$40-50$	$50-60$	$60-70$
Frequency	$2$	$10$	$40$	$25$	$13$	$10$

(in $.7$)