1.

From 1, 2, 3, …, 320 one number is selected at random. Find the probability that it is either a multiple of 7 or a multiple of 3.(a) 72%(b) 42.5%(c) 12.8%(d) 63.8%This question was addressed to me by my school principal while I was bunking the class.The origin of the question is Discrete Probability topic in portion Discrete Probability of Discrete Mathematics

Answer»

The correct choice is (B) 42.5%

To elaborate: Number of MULTIPLES of 7=45 and number of multiples of 3=10^6 and number of numbers which are multiples of both 7 and 3 = 15 Thus, P (selecting either a multiple of 7 or a multiple of 3) = \(\FRAC{45}{320} + \frac{106}{320} – \frac{15}{320} = \frac{136}{320} = \frac{2}{5}\) = 0.425 or 42.5%.



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