The number of ways in which 5 boys and 4 girls can sit in a row so that all the girls come together and 2 particular girls never be together is

1/n!+1/(n+1)!1/(n+2)! =

If ^(m+n)P₂ = 90, ^(m-n)P₂ = 30 then (m,n) =

20 passengers are to travel by a double decked bus which can accommodate 13 in the upper deck and 7 in the lower deck. The number of ways that they can be distributed is

If a,b,c are the number of 4 digited numbers that can be formed using the digits 2,4,5,7,8 that are divisible by 3,4,5 respectively then the ascending order of a,b,c is

Three persons A,B,C are to speak at a function along with 7 other persons.If the person speak in random order,the probability that A speaks before B and B speaks before C is

The number of ways in which the following prizes be given to a class of 20 boys, first and second in Mathematics, first and second in Physics, first in Chemistry and first in English is

If a is the number of ways of selecting 3 men from 6 men, b is the number of ways of selecting 2 men, 1 woman from 4 me and 2 women and c is the number of ways of selecting 1 man, 2 women from 3 men and 3 women then the ascending of a,b,c is

A gentleman invites a party of 10 guests to a dinner and places 6 of them at one table and the remaining 4 at another, the tables being around. The number of ways in which he can arrange the guests is

A railway carriage can seat 5 each side.The number of ways a party of 4 girls and 6 boys can seat themselves so that the girls may always have the corner seats is