If $^n{P_r} = 840,{\,^n}{C_r} = 35,$ then $n$ is equal to
$1$
$3$
$5$
$7$
How many words of $4$ consonants and $3$ vowels can be formed from $6$ consonants and $5$ vowels
If $'n'$ objects are arranged in a row then the number of ways of selecting three of these objects so that no two of them are next to each othe
Determine the number of $5 -$ card combinations out of a deck of $52$ cards if each selection of $5$ cards has exactly one king.
$\sum \limits_{ k =0}^6{ }^{51- k } C _3$ is equal to
Find the number of words with or without meaning which can be made using all the letters of the word $AGAIN$. If these words are written as in a dictionary, what will be the $50^{\text {th }}$ word?