Page 268 - ICSE Math 7

AT A GLANCE

¾ A random experiment is an activity whose result cannot be predicted in advance.
¾ Each possible result of an experiment is its outcome.
¾ A set of all possible outcomes of an experiment is a sample space. A part or whole of a sample
space is called an event.
¾ Experimental or empirical probability is determined by observing the outcomes of an experiment.

¾ The probability of occurrence of an event is defined as:
Number of outcomes favourable to A
P (Occurrence of event A) =
Total number of outcomes
¾ Experimental probability comes closer and closer to theoretical probability as the number of
trials increases.

MENTAL MATHS

1. Choose the correct answer.

(a) The probability of an event whose likelihood of occurrence and non-occurrence is same is
_________.
1 1
(i) 0 (ii) (iii) (iv) 1
4 2

(b) A bag contains 10 marbles of which 8 are red. One marble is drawn at random. The probability
that it is not red is _________.

8 6 4 2
(i) (ii) (iii) (iv)
10 10 10 10

(c) If a letter is taken out from a bag containing letters of the word “SNAKE”, the probability
of picking A is _________.

1 2 1
(i) (ii) (iii) (iv) 1
5 5 2
(d) If a slip of paper is drawn from a jar containing 12 slips with different months of the year
written on it, then probability of the month starting with letter ‘J’ is _________.

1 2 3 4
(i) (ii) (iii) (iv)
12 12 12 12
(e) If a card is drawn from a well-shuffled deck of 52 playing cards, the probability of it being
both red and black is _________.
1 1
(i) 0 (ii) (iii) (iv) 1
4 2

(f) If a die is thrown once, the sample space not having equally likely outcomes is _________.
(i) {even number, odd number} (ii) {prime number, composite number}
(iii) {number whose value is at most 3, number whose value is at least 4}

(iv) none of these

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