Advertisements
Advertisements
प्रश्न
In a cricket match, a batsman hits a boundary 6 times out of 30 balls he plays.
(i) he hits boundary
(ii) he does not hit a boundary.
उत्तर
The total number of trials is 30.
Remember the empirical or experimental or observed frequency approach to probability.
If n be the total number of trials of an experiment and A is an event associated to it such that A happens in m-trials. Then the empirical probability of happening of event A is denoted by P(A) and is given by
P(A) =`m/n`
(i) Let A be the event of hitting boundary.
The number of times A happens is 6.
Therefore, we have
P(A) =`6/30`
= 0.2
(ii) Let B be the event of does not hitting boundary.
The number of times B happens is30-6=24 .
Therefore, we have
P(B) =`24/30`
= 0.8
APPEARS IN
संबंधित प्रश्न
1500 families with 2 children were selected randomly, and the following data were recorded:-
Number of girls in a family | 2 | 1 | 0 |
Number of families | 475 | 814 | 211 |
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.
An organization 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 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 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.
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 follows: 0 − 20, 20 − 30… 60 − 70, 70 − 100. Then she formed the following table:-
Marks | Number of students |
0 - 20 | 7 |
20 - 30 | 10 |
30 - 40 | 10 |
40 - 50 | 20 |
50 - 60 | 20 |
60 - 70 | 15 |
70 - above | 8 |
Total 90 |
(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.
Define an elementary event.
A big contains 4 white balls and some red balls. If the probability of drawing a white ball from the bag is `2/5`, find the number of red balls in the bag.
what is the probability of getting at least two heads?
Mark the correct alternative in each of the following:
The probability of an impossible event is
In a football match, Ronaldo makes 4 goals from 10 penalty kicks. The probability of converting a penalty kick into a goal by Ronaldo, is
Two coins are tossed 1000 times and the outcomes are recorded as below:
Number of heads | 2 | 1 | 0 |
Frequency | 200 | 550 | 250 |
Based on this information, the probability for at most one head is
A recent survey found that the ages of workers in a factory is distributed as follows:
Age (in years) | 20 – 29 | 30 – 39 | 40 – 49 | 50 – 59 | 60 and above |
Number of workers | 38 | 27 | 86 | 46 | 3 |
If a person is selected at random, find the probability that the person is:
- 40 years or more
- under 40 years
- having age from 30 to 39 years
- under 60 but over 39 years