Find the number of ways in which 5Aprimesand6B′s can be arranged in a row which reads the same backwards and forwards.
Let f(n) be the number of regions in which n coplanar circles can divide the plane. If it is known that each pair of circles intersect in two different points and no three of them have common points of intersection, then (i) f(20)=382 (ii) f(n) is always an even number (iii) f−1(92)=10 (iv) f(n) can be odd
A box contains 2 white balls, 3 black balls & 4 red balls. In how many ways can three balls be drawn from the box if atleast one black ball is to be included in draw (the balls of the same colour are different)
The total number of divisor of 480 that are of the form 4n+2,n≥0, is equal to a. 2 b. 3 c. 4 d. none of these
How many 3-digit numbers can be formed from the digits 1, 2, 3, 4 and 5 assuming that
(i) repetition of the digits is allowed?
(ii) repetition of the digits is not allowed?