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Q:

A number is selected at random from the numbers 1 to 30. What is the probability that it is divisible by either 3 or 7 ?

A) 1/30 B) 2/30
C) 1/25 D) 1/2

Answer:   A) 1/30



Explanation:

Let A be event of selecting a number divisible by 3. B be the event of selecting a number divisible by 7.

  Proability tutorial

 A = { 3, 6, 9, 12, 15, 18, 21, 24, 27, 30 }, so n(A)=10
 B = { 7, 14, 21, 28 }, n(B)= 4 

Probability problems 

Since A and B are not mutually exclusive So :

Probability addition rule

Probability problems

Subject: Probability
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