NCERT Class 9 Solutions: Probability (Chapter 15) Exercise 15.1-Part 2 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Equation of Theoretical Probability

Q-4 Three coins are tossed simultaneously 200 times with the following frequencies of different outcomes:

Three Coins Are Tossed Simultaneously 200 Times
Outcome3 heads2 heads1 headNo head

If the three coins are simultaneously tossed again, compute the probability of heads coming up.


Number of times 2 heads come up

Total number of times the coins were tossed

Required probability

Q-5 An organisation selected 2400 families at random and surveyed them to determine a relationship between income level and the number of vehicles in a family. The information gathered is listed in the table below:

Monthly Income and Vehicles Per Family Are Given
Monthly income (in ₹)Vehicles per family
012Above 2
Less than 700010160250
7000 - 100000305272
10000 - 130001535291
13000 - 1600024695925
16000 or more15798288

Suppose a family is chosen. Find the probability that the family chosen is

I. Earning per month and owning exactly vehicles.

II. Earning or more per month and owning exactly vehicle.

III. Earning less than per month and does not own any vehicle.

IV. Earning per month and owning more than vehicles.

V. Owning not more than vehicle.


Total numbers of families

Solution I:

Numbers of families earning per month

Owning exactly vehicles

Required probability

Solution II:

Number of families earning or more per month

Owning exactly vehicle

Required probability

Solution III:

Number of families earning less than per month

Does not own any vehicle

Required probability

Solution IV:

Number of families earning per month

Owning more than vehicles

Required probability

Solution V: Number of families owning not more than vehicle

Required probability