retagged by
448 views
1 votes
1 votes

1) Two coins are tossed.What is the probability of getting one head and one tail ? WKT ANS IS 2/4=1/2

2) A coin is tossed twice.What is the probability of getting one head and one tail ? WKT ANS is 2/4=1/2

3) A bag has 3 red balls and 4 green balls.Two balls are picked from the bag randomly.What is the probability of getting one red and one green ? ANS GIVEN IS (3/7*4/6)....WHY NOT (3/7*4/6)+(4/7*3/6)

I MEAN WHY WE ARE CONSIDERING THE ORDER FOR 1) AND 2) BUT NOT FOR 3)

THAT IS IN 1) AND 2) ......{HEAD,TAIL} AND {TAIL,HEAD} ARE TREATED DIFFERENTLY BUT IN 3) BOTH {R,G} AND {G,R} ARE TREATED SAME......WHY ???

please explain I am getting confused here ....

retagged by

1 Answer

Best answer
3 votes
3 votes

Second QS:

  • We have 4 events
  • All the events are equally likely with probability $ p = 0.25$
  • Therefore total probability = $\sum p = 1$
  • Required probability = $\begin{align*} &\frac{p+p}{\sum p} = 0.5 \\ \end{align*}$

First QS:

  • Almost same as Second QS:
  • Required probability = $\begin{align*} &\frac{p+p}{\sum p} = 0.5 \\ \end{align*}$

Third QS:

  • $4$ possible events.
  • They are not all equally likely.
  • $\begin{align*} &p_1 = \frac{3}{7}*\frac{2}{6} \;,\; p_2 = \frac{3}{7}*\frac{4}{6} \;,\; p_3 = \frac{4}{7}*\frac{3}{6} \;,\; p_4 = \frac{4}{7}*\frac{3}{6} \\ \end{align*}$
  • $\begin{align*} \sum p_i = 1 \end{align*}$
  • Required probability  = $\begin{align*} \frac{p_2+p_3}{\sum p_i} = \frac{4}{7} \end{align*}$
selected by

Related questions

4 votes
4 votes
2 answers
1
Ruturaj Mohanty asked Dec 27, 2018
3,177 views
A book contains $100$ pages. A page is chosen at random. What is the chance that the sum of the digits on the page is equal to $8$?$0.08$$0.09$$0.90$$0.10$
0 votes
0 votes
0 answers
2
Vicky rix asked Feb 27, 2017
314 views
i am not able to understand "when to use poisson random variable" concept comparing to other random variables ...can somebody explain ....
0 votes
0 votes
1 answer
3
Vicky rix asked Feb 27, 2017
411 views
ANSWER I AM GETTING : (0.5) / [1-(0.5n)]ANSWER GIVEN : (0.5) / [ 1-(0.5n-1) ]
0 votes
0 votes
0 answers
4