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You have two strings whose only known property is that when you light
one end of either string it takes exactly one hour to burn. The rate at
which the strings will burn is constant and strings are identical.
How do you measure 45 minutes?
That's how to measure 45 minutes!
What was the challenge?
1.
Burn both the ends of 1st string and 1 end of other string.
2. After 30 minutes, 1st string will be burnt out and half of the other string will be burnt out.So far we have counted 30 minutes.
3. Now burn the other end of 2nd end. It will take 15 minute to burnt out totally. This way, we have counted 30 + 15 = 45 minutes using 2 strings.
Mr. Yellow, Mr. Black and Mr. Brown, three best friends since
kindergarten meet in a function after 5 years. The three of them are
wearing either a Yellow, Black or Brown shirt.
After giving each other a friendly hug, Mr. Black says, "Hey, did you
notice that we are wearing a different colored shirt than our names!"
The man wearing a Brown shirt said, "Wow I certainly did not notice that but you are right Mr. Black."
Based on this conversation, can you find our who was wearing which colored shirt?
Know color of each person's shirt here!
Read this conversation first!
One thing is sure that Mr.Black is not wearing the BLACK shirt. He is also not wearing BROWN as well as we found the other person wearing the BROWN colored shirt is agreed with the statement made by Mr.BLACK in a conversation. So only color left is the YELLOW & Mr. Black must be wearing that.
Now, the colors left are BROWN and BLACK and persons left are Mr. Yellow and Mr.Brown. Since, each of them wearing different color than his surname, Mr. Brown must be wearing the BLACK shirt. And hence, Mr. Yellow is wearing the BROWN shirt!
To conclude, Mr.Black is wearing YELLOW shirt, Mr. Brown is wearing BLACK shirt & Mr. Yellow must be wearing BROWN shirt.
Five students - Adam, Cabe, Justin, Michael and Vince appeared for a
competitive exam. There were total five questions asked from them from
which were two multiple choice questions (a, b or c) and three were
true/false questions. Their answers are given as follows:
Name I II III IV V
Cabe c b True True False
Adam c c True True True
Justin a c False True True
Michael b a True True False
Vince b c True False True
Also, no two students got the same number of correct answers. Can you
tell the correct answer? Also, what are their individual score?
What was the test?
There are 2 possibilities of scores & that are either 0,1,2,3,4 or 1,2,3,4,5. First of all, let's arrange students' responses in order like below.
 |
| Table 1 |
What we notice here is that, there are few responses to same question by different student matching.
For the Question III, only Justin given different answers than other.
Case 1 : If we assume Justin's answer is correct then rest of all are wrong in response to Question III. That means either maximum score in test is 4 or Justin himself has scored 1 to 5.
Let's test that apart from Justin who can have score of 4. If any body other scores 4 then he must share at least 3 similar answers with other (excluding Answer III; refer image below). Only Adam has exact 3 matching responses with Justin.
 |
| Table 2 |
If Adam's score is 4 (Answers to I, II, IV, V are correct) then, Justin too would score 4 (Answers to II, III, IV,V are correct) since Adam & Justin have same responses to Questions II, IV,V).
If nobody scoring as 4 then Justin can have score of 4 or 5.
Case 1.1 : If his score is 4 then there has to be somebody has to be there scoring 0. Now Vince and Adam has at least 2 responses matching with the Justin. That means they can't score 0 since even 1 answer is wrong as Justin the other must be correct as Justin. Michael or Cabe can have 0 score in the case. If anybody of them has score 0 then answer as a TRUE to the Question IV is incorrect i.e. correct Answer IV is FALSE. So Justin is WRONG in Answer IV only. In short, a, c, FALSE, FALSE, TRUE is correct combination of answers. But thing is here in the case both Michael and Cabe would have score 0! Hence Justin's score can't be 4 too.
Case 1.2 : If Justin's score is 5, then a, c, FALSE, TRUE, TRUE are the right answers. No one would score 4 in that case with 3 as second highest by Adam.
An eccentric professor used a unique way to measure time for a test lasting 15 minutes.
He used just two hourglasses. One measured 7 minutes and the other 11 minutes.
During the whole time he turned the hourglasses only few times.
How did he measure the 15 minutes?
Couple of methods to count 15 minutes.
Source
