"Everything should be made as simple as possible, but not simpler."
- Albert Einstein
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?
[A].
1
2
[B].
2
5
[C].
8
15
[D].
9
20
Answer: Option D
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}.
Let E = event of getting a multiple of 3 or 5 = {3, 6 , 9, 12, 15, 18, 5, 10, 15, 20}.
P(E) = 1/2.
Is this correct? Please give your thoughts on this.
Karthik said:
(Thu, Jul 22, 2010 03:18:19 AM)
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.
Veeru said:
(Sun, Sep 26, 2010 03:17:02 PM)
Sundar & Manju thought wrong because 15 already be consider.
So ans will be 9/20.
Sneha said:
(Mon, Sep 27, 2010 05:17:12 AM)
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).
Praveen Kumar Gautam said:
(Fri, Oct 1, 2010 06:46:51 AM)
Answer will be 9/20, because 15 already be considered, so it can not be consider next time. So Sundar & Manju thought wrong.
Souravbaidya said:
(Fri, Nov 26, 2010 02:44:20 AM)
A circular dartboard of radius 1 foot is at a distance of 20 feet from you. You throw a dart at it and it
hits the dartboard at some point Q in the circle. What is the probability that Q is closer to the center
of the circle than the periphery?
a) 0.75 b) 1 c) 0.5 d) 0.25
Pawan said:
(Thu, Dec 2, 2010 06:52:11 AM)
Hi Guys ..
according to me the answer is 2/5
A = multiple of 3
B = multiple of 5
P(A U B) = P(A) + P(B) - P(A n B)
n(A) = 6 ( 3,6,9,12,15,18)
n(B) = 3 (5,10,15)
n (A n B) = 1 (15 --> this comes in both)
Hence, prob = 6/20 + 3/20 - 1/20 = 8/20 = 2/5
Murugesh said:
(Sat, Jan 1, 2011 10:47:17 AM)
hi pawan,
according to your assumption, you had missed the 20 in n(B)
so n(B)={5,10,15,20}
then P(B)=4/20
Hence P(AUB)=6/20+4/20-1/20=9/20.
Dipesh said:
(Wed, Jan 26, 2011 05:04:48 AM)
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)
Satyendra Shukla said:
(Mon, Feb 7, 2011 04:34:01 AM)
Answer will be 9/20, because 15 already be considered, so it can not be consider next time.
Dharmesh Patel said:
(Wed, Feb 16, 2011 01:53:28 AM)
Yes answer is Only and only 9/20.
Sugnya said:
(Fri, Feb 18, 2011 03:42:40 AM)
The answer is 1/2 because if there is same number we should include it. This not union or intersection model.
Albert said:
(Sat, Mar 26, 2011 01:41:12 AM)
Final answer is 9/20
Kiruba said:
(Sun, May 15, 2011 02:24:49 PM)
Thanks sneha. Ans is 9/20.
Rach said:
(Thu, May 26, 2011 12:56:36 PM)
Circular board of i feet has area Pi. The area of the region containing all points which are closed to center than to periphery will be Pi/4. Hence the proportion to hit near the center is 1/4=.25. So D is the correct answer.
Rahul said:
(Tue, May 31, 2011 04:27:28 PM)
@rach.
Hai rach I didn't get you. Can you please explain clearly.
n(E) = number of possible events
n(S) = total number of samples
Eg. Tickets which is numbered 1 to 20 is n(S)
The possible tickets drawn which has number multiple of 3 and 5 is n(E).
Arun said:
(Tue, Aug 23, 2011 12:32:58 PM)
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}.
Aruna said:
(Tue, Sep 20, 2011 07:28:37 PM)
Hi murugesh what you explained is clear. Thank you.
Sohail said:
(Wed, Sep 21, 2011 12:44:08 AM)
15 creates a big confusion.
Because my answer is 1/2...:(
p(3)={3,6,9,12,15,18}
p(5)={5,10,15,20}
P(3u5)=p(3)+p(5)
=6/20+4/20
=6+4/20
=10/20
=1/2
Aneel said:
(Mon, Oct 3, 2011 02:53:27 PM)
Thank you murugesh for clarifying the doubt.
Saurav said:
(Wed, Oct 12, 2011 11:51:50 PM)
Please give me logical solution of the following problem.
A lady has fine gloves and hats in her closet- 18 blue, 32 red, and 25 yellow. The lights are out and it is totally dark. In spite of the darkness, she can make out the difference between a hat and a glove. She takes out an item out of the closet only if she is sure that if it is a glove. How many gloves must she take out to make sure she has a pair of each color?
a) 50 b) 8 c) 60 d) 42
Thanks.
Subrata said:
(Thu, Nov 10, 2011 04:05:05 PM)
Hi
The answer is 9/20
A={3,6,9,12,15,18}
B={5,10,15,20}
P(A)=6/20
P(B)=4/20
A intersection B = {15}
P(A intersection B) = 1/20
P(A U B)= P(A)+P(B)-P(A intersection B)
= 6/20 + 4/20 - 1/20
= 9/20
P(E) =