In a row of trees,one tree is fifth from either end of the row. How many trees are there in the row?

In a class of $20$ students, Alisha's rank is $15^{th}$ from the top. Manav is $4$ ranks above Alisha. What is Manav's rank from the bottom (in $^{th}$)?

In a class of $60$ students, where girls are twice the number of boys, Kamal ranked $17^{th}$ from the top. If there are $9$ girls ahead of Kamal, how many boys are after him in rank?

$A$ 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?

How many $3$s are there in the following number sequence which are immediately preceded by $6$ but not immediately followed by $7$?
$2, 3, 7, 4, 3, 5, 6, 3, 7, 4, 6, 3, 8, 9, 6, 5, 1, 8, 3, 7, 2, 4, 2, 8, 6, 3, 9$

Manisha ranked sixteenth from the top and twenty-ninth from the bottom among those who passed an examination. Six boys did not participate in the competition and five failed in it. How many boys were there in the class?