NCERT Class 9 Solutions: Probability (Chapter 15) Exercise 15.1-Part 2

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Equation of theoretical probability

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

Outcome

3 heads

2 heads

1 head

No head

Frequency

23

72

77

28

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

Solution:

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 RS)

Vehicles per family

0

1

2

Above 2

Less than 7000

10

160

25

0

7000-10000

0

305

27

2

10000-13000

1

535

29

1

13000-16000

2

469

59

25

16000 or more

1

579

82

88

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.

Solution:

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