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PROBABILITY

  • Objective Questions based on different types of events & Equally likely Outcomes

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Q. Complete the following statements.

(i) Probability of an event E + Probability of the event ‘not E’ = ____.

(ii) The probability of an event that cannot happen is ______. Such an event is called __________________.

  1. The probability of an event that is certain to happen is ____. Such an event is called _____________________.
  2. The sum of the probabilities of all the elementary

events of an experiment is _____.

  1. The probability of an event is greater than or

equal to ____ and less than or equal to ___

1

0

Impossible event

sure / certain event

1

1

0

1

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Q. Which of the following experiments have equally likely

outcomes? Explain

(i) A driver attempts to start a car. The car starts or does not start.

  1. A player attempts to shoot a basketball. She/he shoots or

misses the shot.

(iii) A trial is made to answer a true-false question. The answer is right or wrong.

(iv) A baby is born. It is a boy or a girl.

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Sol. (iii) and (iv) have equally likely outcomes.

This statement is not complete

Because we don’t know anything about the car or the driver

To say for an incomplete statement whether it has equally likely outcomes is not possible

This experiment does not have equally likely outcomes

This statement is incomplete

Because we don’t know the ability of the player

This experiment does not have equally likely outcomes

Answer to any true or false question is either right or wrong

This experiment has equally likely outcomes

Whenever a baby is born it is either a boy or a girl

This experiment has equally likely outcomes

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Q. Which of the following cannot be the probability of an event?

Sol.

(B) – 1.5

4. If P(E) = 0.05, what is the probability of ‘not E’ ?

Sol.

= 1

= 1 – P (E)

= 1 – 0.05

= 0.95

P(E) = 0.05

(B) – 1.5 (C) 15% (D) 0.7

(A)

∴

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We have just learnt probability of any event lies between 0 and 1

It cannot be less than 0 or it cannot be more than 1

We know one relation between probability of E and probability of not E.

Probability of an event can never be negative

∴ The probability of not E is 0.95