Question

Cards number 1 to 20 are mixed up and then a cards are drawn are random.What is the probability thats the cards drawn has a number which is multiple of 3 or 5

Answer 1

9/20

Step-by-step explanation:

n (S)=20 -(given)

multiple of 3=3,6,9,12,15,18

multiple of 5=5,10,15,20

(both have common 15)

therefore,

let A be the set of multiple of 5 and 3

A=(3,5,6,9,10,12,15,18,20)

n (A)=9

therefore,

p (A)=n (A)/n (S)

p(A)=9/20

Answer 2

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Total number of outcomes = 20

Let E = Event  of getting multiple of 3 or 7.

Cards marked with multiple of 3 or 5 are 3, 5, 6, 9, 10, 12, 15, 18 and 20.

Number of outcome favourable to E = 9

Probability (E) = Number of favourable outcomes / Total number of outcomes

P(E) = $\frac{9}{20}$

 

Hence, the required probability of getting a multiple of 3 or 5, P(E) = $\large\frac{9}{20}$