Q60 of 66 Page 15

A bag contains 15 white and some black balls. If the probability of drawing a black ball from the bag is thrice that of drawing a white ball, find the number of black balls in the bag.[CBSE 2017]

Let the no of black balls be 'x'


No of white balls = 15


Total no of balls = 15 + x


Now, we know that


Probability of an event


⇒ P(getting a white ball)


⇒ P(getting a black ball)


Given,


P(getting a black ball) = 3 × P(getting a white ball)



⇒ x = 45


Hence, No of black balls is 45.

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There are 100 cards in a bag on which numbers from 1 to 100 are written. A card is taken out from the bag at random. Find the probability that the number on the selected card (i) is divisible by 9 and is a perfect square (ii) is a prime number greater than 80.[CBSE 2016]

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Two different dice are thrown together. Find the probability that the numbers obtained

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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

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A card is drawn at random from a well - shuffled deck of playing cards. Find the probability that the card drawn is

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(iii) neither a jack nor a king


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