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 4 of 11.

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?

Shashi said:   8 years ago
Since the number of events are 20.

So possible events are {3,6,9,12,15,18,5,10,20}.
So answer is 9/20.

Nithya Arun said:   8 years ago
How can we calculate the same problem with big numbers? i.e if tickets numbered 1-200.

Vikram reddy said:   8 years ago
No, here 15 is repeated in 3&5 so the answer is 2/5.

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.

Arjun patidar said:   8 years ago
Ans is 9/20 because,

P(A) + P(B) - P(A andB) = P(A OR B )

For p (a) outcome are divide to 20 for getting multiple of 3 we get in rational left after point so 6.
Then also of 5 we get 4 numbers can multiple of five.
After it puts in probability case such as 6/20 + 4/20 - 1/20.
1/20 comes to get no. of both that is only one number 15 and also use short cut as take the LCM of 3&5 we get 15, divide 20 by it to get some thing 1. Left fraction we get 1/ 20 or 1 out of 20 put all in formula.

6/20 + 4/20 - 1/20 = 9/20 answer.

Ravi said:   8 years ago
According to me, From 1 to 20, numbers its 1, 2, 3, 4....., 19, 20 then number which is a multiple of 3 or 5.

Lets take 3 (3, 6, 9, 12, 15, 18 and 5 = (5, 10, 15, 20).

So in 3 we have 6 and 5 we have 4 so it's 6/20 and 4/20 and 1/20.

Solution = 6 + 4 - 1/20 == 9/20 answer.

Ravi said:   8 years ago
According to me, From 1 to 20, numbers its 1, 2, 3, 4....., 19, 20 then number which is a multiple of 3 or 5.

Lets take 3 (3, 6, 9, 12, 15, 18 and 5 = (5, 10, 15, 20).

So in 3 we have 6 and 5 we have 4 so it's 6/20 and 4/20 and 1/20.

Solution = 6 + 4 - 1/20 == 9/20 answer.

Ujjwal shukla said:   8 years ago
Find the probability that a number from 1 to 300 is divisible by 3 or 7.

Can anyone answer this question.

Kavana said:   8 years ago
From 1 to 340, the probability of getting multiples of 8 and 5 is? Please answer this question.


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