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?
1
2
2
5
8
15
9
20
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 5 of 11.

Dipesh said:   1 decade ago
Yes, answer is 9/20. We should not consider a number more than one time (15 is a multiple of 3 and 5. So, it cannot be used more than once)

Isha said:   8 years ago
Please help me to solve this-

A number is selected at random from first 50 number. Find the probability that it is a multiple of 3 and 4.

Arun said:   1 decade ago
I can't understand.

P (e) ={3, 6, 9, 12, 15, 18, 5, 10, 20}.

We multiplying p (e) with s then we don't want to multiply s={7, 8 to 18}.

Deepika Balaji said:   7 years ago
Can anyone help me in solving this problem. What is the probability of getting at least one six in a single throw of three unbiased dice?

Tanya said:   2 years ago
Yes, 9/20 is the correct option because 15 is a multiple of both 3 and 5.
So we considered it only once (either with 3 or either with 5).
(26)

Karthik said:   2 decades ago
No. You are wrong Sundar.

Because, 15 has already consider once so there is no need to consider it again.

So the answer is 9/20.

Naina said:   8 years ago
A coin is tossed live times. What is the probability that there is at the least one tail?

Can anyone help me with this question?

Praveen Kumar Gautam said:   1 decade ago
Answer will be 9/20, because 15 already be considered, so it can not be consider next time. So Sundar & Manju thought wrong.

Sagaana said:   7 years ago
How to solve the same problem when the 1000 tickets mixed in the pack what is the probability of getting multiples of 3 and 5?

ANIL CHAUHAN said:   1 decade ago
A(n)={3,6,9,12,15,18}

B(n)={5,10,15,20}

P(AuB)=P(A)+P(B)-P(A intersection B)

P(AuB)=6/20+4/20-1/20

P(AuB)=9/20.


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