Find the best tutors and institutes for Class 9 Tuition
Search in
A teacher wanted to analyse the performance of two sections of students in a mathematics test of 100 marks. Looking at their performances, she found that a few students got under 20 marks and a few got 70 marks or above, So she decided to group them into intervals of varying sizes as fallows:
(i) Find the probability that a student obtained less than 20% in the mathematics
test.
(ii) Find the probability that a student obtained marks 60 or above.
For less than 20 probablity is 7/90
And greater than 60 is (15+8)/90=23/90
To know the opinion of the students about the subject statistics, a survey of 200
students was conducted. The data is recorded in the following table.
Find the probability that a student chosen at random
(i) likes statistics,
(ii) does not like it.
likes prob = 135/200 = 27/40
dislike prob = 65/200 = 13/40
The distance (in km) of 40 engineers from their residence to their place of work were found as follows:
What is the empirical probability that an engineer lives:
(i) less than 7 km from her place of work?
(ii)more than or equal to 7 km from her place of work?
(iii) within km from her place of work?
(i) Total number of engineers = 40
Number of engineers living less than 7 km from their place of work = 9
Hence, required probability that an engineer lives less than 7 km from her place of work,
(ii) Number of engineers living more than or equal to 7 km from their place of work = 40 − 9 = 31
Hence, required probability that an engineer lives more than or equal to 7 km from her place of work, 
(iii) Number of engineers living within 
km from her place of work = 0
Hence, required probability that an engineer lives within km from her place of work, P = 0
Eleven bags of wheat flour, each marked 5 kg, 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.
prob = 7/11
A study was conducted to find out the concentration of sulpur di oxide in air in parts per million(ppm) of a certain city. The data obtained for 30 days is as follows:
you were asked to prepare a frequency distribution table, regarding the concentration of sulphur dioxide in the air in parts per million of a certain city for 30 days. Using this table, find the probability of the concentration of sulphur dioxide in the interval 0.12 - 0.16 on any of these days.
Total No of days = 30
No of days in interval 0.12-0.16 = 2
so probability for air pollution between 0.12-0.16 interval = 2 / 30 =1 /15
The blood group of 30 students of class VIII were 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.
you were asked to prepare a frequency distribution table regarding the blood groups of 30 students of a class. Use this table to determine the probability that a student of this class, selected at random, has blood group AB.
1/10
In a cricket match, a batswoman hits a boundary 6 times out of 30 balls she plays. Find the probability that she did not hit a boundary.
If the batswoman hits a boundary 6 times out of 30 balls she plays, then it means she doesn't hit a boundary 24 times out of 30 balls she plays.
So, the probability that she did not hit a boundary = 24/30 = 4/5.
1500 families with 2 children were selected randomly, and the following data were recorded:
Compute the probability of a family, chosen at random, having
(i)2 girls
(ii) 1 girl
(iii) No girl
Also check whether the sum of these probabilities is 1.
(i) Total number of families is 1500.
Number of families that are having 2 girls is 475.
So, the probability of a family, chosen at random, having 2 girls is 475/1500 = 19/60.
(ii) Total number of families is 1500.
Number of families that are having 1 girl is 814.
So, the probability of a family, chosen at random, having 1 girl is 814/1500 = 407/750.
(iii) Total number of families is 1500.
Number of families that are having no girl is 211.
So, the probability of a family, chosen at random, having no girl is 211/1500.
And, 19/60 + 407/750 + 211/1500 = 1.
In a particular section of class IX, 40 students were asked about the monrh of their birth and the following graph was prepared for the data so obtained.
Find the probabilty that a student of the classwas born in the month of August.
Total No. of Students = 40
Total No. of Students born in August = 6
so probability of born in Aug = 6/40 = 3/20
Three coins are tossed simultaneously 200 times with the following frequencies of different outcomes:
If the three coins are simultaneously tossed again, compute the probability of 2 heads coming up.
Number of times three coins are tossed simultaneously = 200
Number of times 2 heads came up = 72
So, the probability of 2 heads coming up when the three coins are simultaneously tossed again = 72/200 = 18/25
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:
Suppose a family is chosen. Find the probability that the family chosen is
(i) earning Rs. 10000 – 13000 per month and owning exactly 2 vehicles.
(ii) earning Rs. 16000 or more per month and owning exactly 1 vehicle.
(iii) earning less than Rs. 7000 per month and does not own any vehicle.
(iv) earning Rs. 13000 – 16000 per month and owning more than 2 vehicles.
(v) owning not more than 1 vehicle.
(i) Total number of families = 2400
Families with earning of Rs. 10,000 – 13,000 per month and owning exactly 2 vehicles = 29.
So, the probability that the family chosen is earning Rs. 10,000 – 13,000 per month and owning exactly 2 vehicles = 29/2400
(ii) Total number of families = 2400
Families with earning of Rs. 16,000 or more per month and owning exactly 1 vehicle = 579.
So, the probability that the family chosen is earning Rs. 16,000 or more per month and owning exactly 1 vehicle = 579/2400
(iii) Total number of families = 2400
Families with earning of less than Rs. 7,000 per month and does not own any vehicle = 10.
So, the probability that the family chosen is earning less than Rs. 7,000 per month and does not own any vehicle = 10/2400 = 1/240
(iv) Total number of families = 2400
Families with earning of Rs. 13,000 – 16,000 per month and owning more than 2 vehicles = 25.
So, the probability that the family chosen is earning Rs. 13,000 – 16,000 per month and owning more than 2 vehicles = 25/2400 = 1/96.
(v) Total number of families = 2400
Families owning not more than 1 vehicle = 10+0+1+2+1+160+305+535+469+579 = 2062
So, the probability that the family chosen is owning not more than 1 vehicle = 2062/2400 = 1031/1200.
How helpful was it?
How can we Improve it?
Please tell us how it changed your life *
Please enter your feedback
UrbanPro.com helps you to connect with the best Class 9 Tuition in India. Post Your Requirement today and get connected.
Find best tutors for Class 9 Tuition Classes by posting a requirement.
Get started now, by booking a Free Demo Class
