Aptitude - Probability - Discussion
Discussion Forum : Probability - General Questions (Q.No. 1)
1.
Tickets numbered 1 to 20 are mixed up and then a ticket is drawn at random. What is the probability that the ticket drawn has a number which is a multiple of 3 or 5?
Answer: Option
Explanation:
Here, S = {1, 2, 3, 4, ...., 19, 20}.
Let E = event of getting a multiple of 3 or 5 = {3, 6 , 9, 12, 15, 18, 5, 10, 20}.
 P(E) = |
n(E) | = | 9 | . |
| n(S) | 20 |
Discussion:
107 comments Page 7 of 11.
Santosh said:
1 decade ago
Yah by using P(AUB)formula we can calculate this, So no doubt persists-P(A)=6/20, P(B)=4/20,and P(A^B)=1/20(since 15 common for 3,5),
Finally answer is 6/20+4/20-1/20 = 9/20.
Finally answer is 6/20+4/20-1/20 = 9/20.
Aarti Gosavi said:
1 decade ago
There are three drawers in a table. One drawer contains two gold coins another drawer contains two silver coins and third drawer contains one silver and one gold coin. One of the drawers is pulled out and a coin is taken out. It turns out to be a silver. What is probability of drawing a gold coin if one of the other two drawers is pulled out next and one of the coin in it is drawn at random?
Nikhil Merwade said:
1 decade ago
Why can't we use the formula of nCr...??...
1 ticket can be selected from 20 tickets in 20C1 ways.
Ticket removed is a multiple of 3 or 5 will be 20C6 * 20C4
Answer will be (20C6 * 20C4)/20C1...
Why can't this be proper method?
1 ticket can be selected from 20 tickets in 20C1 ways.
Ticket removed is a multiple of 3 or 5 will be 20C6 * 20C4
Answer will be (20C6 * 20C4)/20C1...
Why can't this be proper method?
Saiful Islam said:
1 decade ago
Actually, I don't understand your explanation boss. Please explain elaborately. How can it will be 9/20?
ABHISEK MUKHERJEE said:
1 decade ago
Use just simple probability formula,
P(A+B) = P(A)+P(B)-P(AB).
P(A+B) = P(A)+P(B)-P(AB).
Rupali said:
1 decade ago
Hi all.
Can anyone explain how 1/20 come?
Can anyone explain how 1/20 come?
Goutam said:
1 decade ago
Yes answer is 9/20 because if we consider two event A & B which are multiple of 3 and 5 respectively then the required event is P(AuB)= P(A)+ P(B)-p(AB) = 6/20+4/20-1/20 = 9/20.
Niha said:
1 decade ago
Yes, 9/20 is the correct answer.
Sharada said:
1 decade ago
15 also should come in the list right?
Adhamki dileep kumar said:
1 decade ago
Sample space p(s) = 20c1 = 20.
Events occurred p(e) = (3,6,9,12,15,18,5,10,15,20) = 10.
= (3,6,9,12,15,18,5,10,20)=9
Probability = p(e)/p(s).
= 9/20.
Events occurred p(e) = (3,6,9,12,15,18,5,10,15,20) = 10.
= (3,6,9,12,15,18,5,10,20)=9
Probability = p(e)/p(s).
= 9/20.
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