Find the median of the following frequency distribution:

Class	$0-20$	$20-40$	$40-60$	$60-80$	$80-100$
Frequency	$5$	$15$	$20$	$18$	$2$

Find the median of the following frequency distribution:

Class	$60-70$	$70-80$	$80-90$	$90-100$	$100-110$	$110-120$
Frequency	$5$	$15$	$20$	$30$	$20$	$8$

For a given frequency distribution,the frequencies of the first,second,and third class are $8$,$15$,and $18$ respectively. Then,the cumulative frequency of the third class is $\ldots \ldots \ldots \ldots .$

The lengths of $40$ leaves of a plant are measured correct to the nearest millimetre,and the data obtained is represented in the following table:

Length (in mm)	Number of leaves
$118-126$	$3$
$127-135$	$5$
$136-144$	$9$
$145-153$	$12$
$154-162$	$5$
$163-171$	$4$
$172-180$	$2$

Find the median length of the leaves.

In the formula $M = l + \frac{(\frac{n}{2} - cf)}{f} \times h$ for the median,$f = \ldots \ldots \ldots$

The median of the following frequency distribution is $46$ and the total frequency is $230$. Find the missing frequencies $x$ and $y$.

Class	$10-20$	$20-30$	$30-40$	$40-50$	$50-60$	$60-70$	$70-80$
Frequency	$12$	$30$	$x$	$65$	$y$	$25$	$18$