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A number is selected at random from the numbers 1 to 30 inclusive. What is the p...


Question

A number is selected at random from the numbers 1 to 30 inclusive. What is the probability that it is divisible by 2 or 5?

Options

A) 19/30

B) 3/5

C) 3/10

D) 7/10

The correct answer is D.

Explanation:

From 1 - 30, there are 30 numbers, 15 numbers divisible by 2, 6 numbers divisible by 5
Pr(Divisible by 2) = \(\cfrac{15}{30} = \cfrac{1}{2}\)
Pr(Divisible by 5) = \(\cfrac{6}{30} = \cfrac{1}{5}\)
Pr(Divisible by 2 or 5) = \(\cfrac{1}{2} + \cfrac{1}{5} = \cfrac{7}{10}\)

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Dicussion (1)

  • From 1 - 30, there are 30 numbers, 15 numbers divisible by 2, 6 numbers divisible by 5
    Pr(Divisible by 2) = \(\cfrac{15}{30} = \cfrac{1}{2}\)
    Pr(Divisible by 5) = \(\cfrac{6}{30} = \cfrac{1}{5}\)
    Pr(Divisible by 2 or 5) = \(\cfrac{1}{2} + \cfrac{1}{5} = \cfrac{7}{10}\)

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