(a) A box contains 40 identical discs which are either red or white. If the probability of picking a red disc is ; Calculate the number of (i) white discs ; (ii) red discs that should be added such that the probability of picking a red disc will be . (b) A salesman bought some plates at N50.00 each. If he sold all of them for N600.00 and made a profit of 20% on the transaction, how many plates did he buy?
Explanation
(a) (i) No of red discs = Total no of discs = 40 No of white balls = 40 - 10 = 30 (ii) Let the number of red balls to be added = z Therefore, adding 5 red discs, the probability of picking a red disc = . (b) CP of a plate = N50.00 Let the number of plates be x
