What is the probability that she takes out

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A bag contains a red ball, a blue ball and a yellow ball, all the balls being of the same size. Anjali takes out a ball from the bag without looking into it. What is the probability that she takes out
(i) yellow ball?
(ii) red ball?
(iii) blue ball?

Solution:

Number of balls in the bag = 3.
(i) Probability of yellow ball = \\ \frac { 1 }{ 3 }
(ii) Probability of red ball = \\ \frac { 1 }{ 3 }
(iii) Probability of blue ball = \\ \frac { 1 }{ 3 }

A box contains 600 screws, one-tenth are rusted. One screw is taken out at random from this box. Find the probability that it is a good screw.

Solution:

Number of total screws = 600
Rusted screws = \\ \frac { 1 }{ 10 } of 600 = 60
∴ Good screws = 600 – 60 = 540
Probability of a good screw
P(E) = \frac { Number\quad of\quad favourable\quad outcome }{ Number\quad of\quad possible\quad outcome }
= \\ \frac { 540 }{ 600 }
= \\ \frac { 9 }{ 10 }

In a lottery, there are 5 prized tickets and 995 blank tickets. A person buys a lottery ticket. Find the probability of his winning a prize.

Solution:

Number of prized tickets = 5
Number of blank tickets = 995
Total number of tickets = 5 + 995 = 1000
Probability of prized ticket
P(E) = \frac { Number\quad of\quad favourable\quad outcome }{ Number\quad of\quad possible\quad outcome }
= \\ \frac { 5 }{ 1000 }
= \\ \frac { 1 }{ 200 }

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