20 persons are invited for a party. The number of ways in which they and the host can be seated at a circular table, if two particular persons be seated on eitherside of the host is equal to
2 . (18)!
18! . 3!
19! . 2!
None of these
Using the digits 0, 2, 4, 6, 8 not more than once in any number, the number of 5 digited numbers that can be formed, is
16
24
96
120
Let l1 and l2 be two lines intersecting at P. If A1, B1, C1 are points on l1, and A2, B2, C2, D2, E2 are points on l2 and if none of these coincides with P, then the number of triangles formed by these eight points, is :
56
55
46
45
Consider the fourteen lines in the plane given by y = x + r, y = - x + r,where r {0, 1, 2, 3, 4, 5, 6}. The number of squares formed by these lines, whose sides are of length , is
9
16
25
36
S1, S3, ...... ,S10 are the speakers in a conference. If S1 addresses only after S2,then the number of ways the speakers address iS
10!
9!
A three digit numbern is such that the last twodigits of it are equal and differ from the first. The number of such n's is
64
72
81
900
Eight different letters of an alphabet are given. Words of four letters from these are formed.The number of such words with at least one letter repeated is :
The number of natural numbers less than 1000, in which no two digits are repeated, is :
738
792
837
720
9 balls are to be placed in 9 boxes and 5 of the balls cannot fit into 3 small boxes. The number of ways of arranging one ball in each of the boxes is
18720
18270
17280
12780
C.
17280