A box contains 20 cards numbered from 1 to 20. A card is drawn at random from the box. Find the probability that the number on the drawn card is
(i)divisible by 2 or 3
(ii)a prime number
Answers
SOLUTION :
Given : Cards marked with numbers from 1 to 20
Total number of outcomes = 20
(i)Let E1 = Event of getting a number divisible by 2 or 3
Numbers which are divisible by 2 or 3 = 2,3, 4, 6,8, 9, 10,12,14, 15, 16, 18, 20
Number of outcome favourable to E1 = 13
Probability (E1) = Number of favourable outcomes / Total number of outcomes
P(E1) = 13/20
Hence, the required probability of getting a number divisible by 2 or 3 , P(E1) = 13/20 .
(ii) Let E2 = Event of getting a prime number
Prime number from 1 to 20 are: 2,3,5,7,11,13,17,19
Number of outcome favourable to E2 = 8
Probability (E2) = Number of favourable outcomes / Total number of outcomes
P(E2) = 8/20 = 2/5
Hence, the required probability of getting a prime number , P(E2) = 2/5 .
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Step-by-step explanation:
probability=
Number of favourable outcomes
_________________________
Total number of outcomes
Given number of cards = 20. So,
Total number of outcomes ={1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20} =20
(¡)P(E1) = getting number divisible by 2 or 3
Number of favourable outcomes = {2,3,4,6,8,9,10,12,14,15,16,18,20} = 13
P(E1) =13/20
(¡¡)P(E2) = getting a prime number
Number of favourable outcomes = {2,3,5,7,11,13,17,19} = 8
P(E2) = 8/20
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