Cumulative frequency distribution is used to calculate the $\ldots \ldots \ldots$ of a frequency distribution.

The following table gives the distribution of the lifetime of $400$ neon lamps:

Life time (in hours)	Number of lamps
$1500-2000$	$14$
$2000-2500$	$56$
$2500-3000$	$60$
$3000-3500$	$86$
$3500-4000$	$74$
$4000-4500$	$62$
$4500-5000$	$48$

Find the median lifetime of a lamp.

Consider the following frequency distribution:

Class	$0-5$	$6-11$	$12-17$	$18-23$	$24-29$
Frequency	$13$	$10$	$15$	$8$	$11$

The upper limit of the median class is

For the following data,the median class is $\ldots \ldots \ldots$

Class	$0-10$	$10-20$	$20-30$	$30-40$	$40-50$
Frequency	$12$	$18$	$20$	$17$	$13$

Find the median of the following frequency distribution:

Class	$5-10$	$10-15$	$15-20$	$20-25$	$25-30$	$30-35$	$35-40$	$40-45$
Frequency	$5$	$6$	$15$	$10$	$5$	$4$	$2$	$2$

The median of an ungrouped data and the median calculated when the same data is grouped are always the same. Do you think that this is a correct statement? Give reason.