Some boys are sitting in a row. $P$ is sitting fourteenth from the left and $Q$ is seventh from the right. If there are four boys between $P$ and $Q,$ how many boys are there in the row?

If $16 \times 85 = 8651$,what is $73 \times 42$?

Madhu is $18^{th}$ from the left end and Sandhu is $11^{th}$ from the right end of a row of $40$ children. How many children are there between Madhu and Sandhu in the row?

In the following number sequence,how many such even numbers are there which are exactly divisible by its immediate preceding number but not exactly divisible by its immediate following number?
$3, 8, 4, 1, 5, 7, 2, 8, 3, 4, 8, 9, 3, 9, 4, 2, 1, 5, 8, 2$

$(I)$ Kamal is available at home from $12$ noon to $4 \,p.m.$ on Tuesday,Thursday,and Sunday.
$(II)$ His younger brother Navin is available at home on Monday,Thursday,Friday,and Sunday between $10 \,a.m.$ to $2 \,p.m.$
$(III)$ The eldest brother Rajiv is available between $9 \,a.m.$ to $12$ noon on Monday,Wednesday,and Thursday and $2 \,p.m.$ to $4 \,p.m.$ on Friday,Saturday,and Sunday.
For how many days is only one brother available at a particular time in a week?

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