NDA 2017 Maths · Mathematics · Probability · medium

A number is chosen at random from the integers 1 to 30. The probability that it is divisible by 4 or by 6 is

Single correct option

A number is chosen at random from the integers

1

30

. The probability that it is divisible by

4

or by

6

Show answer and solution

Answer: (C) $\frac13$

Multiples of

4

7

; multiples of

6

5

; multiples of both (

12

2

(namely

12

and

24

). Favourable

=7+5-2=10

, so the probability is

\frac{10}{30}=\frac13

. The value

\frac25

forgets to remove the common multiples.

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