The document RD Sharma Solutions Ex-25.1, (Part - 2), Probability, Class 9, Maths Class 9 Notes | EduRev is a part of the Class 9 Course RD Sharma Solutions for Class 9 Mathematics.

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**Q8. The Blood group table of 30 students of class IX is recorded as follows:**

**A, B, O, O, AB, O, A, O, B, A, O, B, A, O, O**

**A, AB, O, A, A, O, O, AB, B, A, O, B, A, B, O**

**A student is selected at random from the class from blood donation. Find the probability that the blood group of the student chosen is:**

**1: A**

**2: B**

**3: AB**

**4: O**

**ANSWER**

BLOOD GROUP | A | B | O | AB | TOTAL |

NUMBER OF STUDENTS | 9 | 6 | 12 | 3 | 30 |

**1.** Probability of a student having blood group

**2. **Probability of a student having blood group

**3.** Probability of a student having blood group

**4.** Probability of a student having blood group

**Q9. Eleven bags of wheat flour, each marked 5kg, actually contained the following weights of flour (in Kg)**

4.97 | 5.05 | 5.08 | 5.03 | 5.00 | 5.06 | 5.08 | 4.98 | 5.04 | 5.07 | 5.00 |

**Find the probability that any of these bags chosen at random contains more than 5 kg of flour.**

**ANSWER:**

Number of bags weighing more than 5kgs = 7

Total no of bags = 11

Probability of having more than 10kgs of rice

**Q10. The following table show the birth month of 40 students in class IX:**

JAN | FEB | MAR | APR | MAY | JUNE | JULY | AUG | SEP | OCT | NOV | DEC |

3 | 4 | 2 | 2 | 5 | 1 | 2 | 5 | 3 | 4 | 4 | 4 |

**Find the probability that a student is born in October**

**ANSWER:**

**1. **Probability that a student is born in the month of October

**Q11. Given below is the frequency distribution table regarding the concentration of SO _{2} in the air in parts per million of a certain city for 30 days.**

Concentration of SO_{2} | 0.00-0.04 | 0.04-0.08 | 0.08-0.12 | 0.12-0.16 | 0.16-0.20 | 0.20-0.24 |

No of days | 4 | 8 | 9 | 2 | 4 | 3 |

**Find the probability of the concentration of SO2 in the interval 0.12-0.16 on any of these days.**

**Answer:**

Total no of days: 30

Probability of concentration of SO_{2} in interval 0.12-0.16

**Q12. A company selected 2400 families at random and surveys them to determine a relationship between income level and the number of vehicles in a home. The information gathered is listed below**

**VEHICLES PER FAMILY:**

Monthly Income | 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 | 29 | 25 |

16000 above | 1 | 579 | 82 | 88 |

** **

**If a family is chosen at random find the probability that the family is:**

**1. Earning Rs 10000 – 13000 per month and owning exactly 2 vehicles.**

**2. Earning Rs 16000 or more per month and owning exactly 1 vehicle.**

**3. Earning less than Rs 7000 per month and does not own any vehicle.**

**4. Earning Rs 13000 – 16000 per month and owning more than 2 vehicles.**

**5. Owning not more than 1 vehicle.**

**6.****Owning at least one vehicle**

**Answer: **

**1.** The probability that the family is earning 10000-13000 and is having exactly 2 vehicles

= 292/400

**2.** The probability that the family is earning 16000 or more and is having exactly 1 vehicle

**3.** The probability that the family is earning less than 7000 and is having no vehicle

**4.** The probability that the family is earning 13000-16000 and is having more than 2 vehicles

**5.** The probability that the family is having not more than one vehicle

**6.** The probability that the family is having atleast one vehicle

**Q13. The following table gives the life time of 400 neon lamps:**

Life time | 300-400 | 400-500 | 500-600 | 600-700 | 700-800 | 800-900 | 900-1000 |

bulbs | 14 | 56 | 60 | 86 | 74 | 62 | 48 |

**A bulb is selected at random. Find the probability that the lifetime of a selected bulb:**

**1. Less than 400 hrs**

**2. between 300-800 hours**

**3. Atleast 700 hours**

**Answers:**

Total number of bulbs = 400

**1.** Probability that the life of the selected bulb is less than 400hrs

**2.** Probability that the life of the selected bulb is between 300-800hrs

**3.** Probability that the life of the selected bulb is atleast 700hrs

**Q14. Given below is the frequency distribution of wages (in Rs) of 30 workers in certain factory:**

Wages | 110-130 | 130-150 | 150-170 | 170-190 | 190-210 | 210-230 | 230-250 |

No of workers | 3 | 4 | 5 | 6 | 5 | 4 | 3 |

**A worker is selected at random. Find the probability that his wages are:**

**1. Less than Rs.150**

**2. Atleast Rs.210**

**3. More than or equal to 150 but less than 210**

**Answer**

Total number of workers = 30

**1.** Probability that the worker wages are less than Rs.150

**2.** Probability that the worker wages are atleast Rs.210

**3.** Probability that the worker wages are more than or equal to 150 but less than 210

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