English

what is the probability of getting at least two heads? - Mathematics

Advertisements
Advertisements

Question

 what is the probability of getting at least two heads?

 
Answer in Brief

Solution

The total number of trials is 200.

Let be the event of getting atleast two heads.

The number of times A happens is 72 + 23 = 95 .

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 is denoted by P (A) and is given by

`P (A) = m/n`

Therefore, we have

`P (A) = 95/200`

          = `19/40`

shaalaa.com
  Is there an error in this question or solution?
Chapter 25: Probability - Exercise 25.2 [Page 16]

APPEARS IN

RD Sharma Mathematics [English] Class 9
Chapter 25 Probability
Exercise 25.2 | Q 8 | Page 16

Video TutorialsVIEW ALL [1]

RELATED QUESTIONS

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.


Two coins are tossed simultaneously 500 times with the following frequencies of different outcomes:
Two heads: 95 times
One tail: 290 times
No head: 115 times
Find the probability of occurrence of each of these events.


1500 families with 2 children were selected randomly and the following data were recorded:

Number of girls in a family 0 1 2
Number of families 211 814 475

 

If a family is chosen at random, compute the probability that it has:
(i) No girl
(ii) 1 girl
(iii) 2 girls
(iv) at most one girl
(v) more girls than boys

Following table shows the birth month of 40 students of class IX.

Jan Feb March April May June July Aug Sept Oct Nov Dec
3 4 2 2 5 1 2 5 3 4 4 4
Find the probability that a student was born in August.

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

Life time
(in hours)
300-400 400-500 500-600 600-700 700-800 800-900 900-1000
Number of lamps: 14 56 60 86 74 62 48

A bulb is selected of random, Find the probability that the  the life time of the selected bulb is:
(i) less than 400
(ii) between 300 to 800 hours
(iii) at least 700 hours.


Define a trial.

 

Define an elementary event.

 

The probability an event of a trial is


A company selected 4000 households at random and surveyed them to find out a relationship between income level and the number of television sets in a home. The information so obtained is listed in the following table:

Monthly income
(in Rs)
Number of Television/household
0 1 2 Above 2
< 10000 20 80 10 0
10000 – 14999 10 240 60 0
15000 – 19999 0 380 120 30
20000 – 24999 0 520 370 80
25000 and above 0 1100 760 220

Find the probability:

  1. of a household earning Rs 10000 – Rs 14999 per year and having exactly one television.
  2. of a household earning Rs 25000 and more per year and owning 2 televisions.
  3. of a household not having any television.

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 under 40 years


Share
Notifications

Englishहिंदीमराठी


      Forgot password?
Use app×