20 cards whose number are from 1 to 20 are mixed after placing in a box. A card is drawn at random and it is found that the number on the card is greater than 11. Find the probability that the number on the card is an even number.

Answer

N/a

Explanation

Here `n(S)=.^(20)C_(1)=20`
Let `E=` event of getting a number greater than 11
`={12,13,14,15,16,17,18,19,20}`
`F=` event of getting an even number
`={2,4,6,8,10,12,14,16,18,20}`
Now `EnnF={12,14,16,18,20}`
and `P(F//E)=(P(FnnE))/(P(E))=(5//20)/(9//20)=5/9`