Rahul ranked ninth from the top and thirty-eighth from the bottom in a class. How many students are there in the class?

In the series,$6, 4, 1, 2, 2, 8, 7, 4, 2, 1, 6, 3, 8, 6, 2, 1, 7, 1, 4, 1, 3, 2, 8, 6$,how many pairs of alternate numbers have a difference of $2$?

Three persons $A, B$ and $C$ are standing in a queue. There are $5$ persons between $A$ and $B$ and $8$ persons between $B$ and $C$. If there are $3$ persons ahead of $C$ and $21$ persons behind $A$, what could be the minimum number of persons in the queue?

$A$ bus for Trivandrum leaves every $30 \,minutes$ from a bus stand. On enquiring,the clerk told a passenger that the bus had already left ten minutes ago and the next bus will leave at $9:35 \,am$. At what time did the clerk give this information to the passenger?

Sangeeta remembers that her father's birthday was certainly after $8^{th}$ but before $13^{th}$ of December. Her sister Natasha remembers that their father's birthday was definitely after $9^{th}$ but before $14^{th}$ of December. On which date of December was their father's birthday?

How many $7$'s are there in the following series which are preceded by $6$ but not preceded by $8$ (i.e.,the sequence $6, 7$ where $6$ is not immediately preceded by $8$)?
Series: $8, 7, 6, 7, 8, 6, 7, 5, 6, 7, 9, 7, 6, 1, 6, 7, 7, 6, 8, 8, 6, 9, 7, 6, 8, 7$