NCERT Class 9 Solutions: Probability (Chapter 15) Exercise 15.1-Part 2 (For CBSE, ICSE, IAS, NET, NRA 2022)
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Q-4 Three coins are tossed simultaneously 200 times with the following frequencies of different outcomes:
| 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 (in ₹) | 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