In a row of girls,Rita and Monika occupy the ninth place from the right end and tenth place from the left end,respectively. If they interchange their places,Rita and Monika occupy seventeenth place from the right and eighteenth place from the left,respectively. How many girls are there in the row?

$(I)$ 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?

Five boys took part in a race. Prabir finished before Mohit but behind Mihir. Suresh finished before Sanchit but behind Mohit. Who won the race?

In the series,$6, 4, 1, 2, 2, 8, 7, 4, 2, 1, 5, 3, 8, 6, 2, 1, 7, 1, 4, 1, 3, 2, 8, 6$,how many pairs of successive numbers have a difference of $2$ each?

If $3^{rd}$ December,$1990$ is Sunday,what day is $3^{rd}$ January,$1991$?

How many numbers from $11$ to $50$ are there which are exactly divisible by $7$ but not by $3$?