This is a simple division series. Each number is divided by 5. Rule = (1st number / 5 = 2nd number) (2nd number / 5 = 3rd number)....Now, (1000 / 5 = 200), (200 / 5 = 40), (40 / 5 = 8)...So answer is a = 8.
Two balls can be drawn from 18 balls in 18C2 Ways, ie 153 ways. One white from 8 white balls can be drawn in 8C1 = 8 ways and one black ball from 10 black can be drawn in 10C1 = 10 ways.∴ n(S) = 153, n(E) = 8 x 10 = 80∴ P(E) = 80/153
EXAMIANS