If $^{12}P_r = 1320$,then $r$ is equal to

How many words can be formed using the letters of the word $INSURANCE$,such that all vowels always come together?

If ${}^n{P_4} : {}^n{P_5} = 1 : 2$,then $n = $

The number of words which can be made out of the letters of the word $MOBILE$ when consonants always occupy odd places is

There were two women participating in a chess tournament. Every participant played two games with the other participants. The number of games that the men played between themselves exceeded the number of games that the men played with the women by $66$. The total number of participants is:

If $^{10}C_r = ^{10}C_{r+2}$,then $^5C_r$ equals: