Great Brain Teasers - Set 2

In the quest to present some of the greatest puzzles and Brain teasers of the past decade, here are five famous puzzles which are simple evergreen at all times. These puzzles are very good in the sense that they make you to think and arrive at a logic for finding the solution. I'm not providing the answers to these Brain Teasers as giving them here would make the puzzle open..I would like the reader to solve the logic puzzle by themselves and post the answer as a comment..So, here we go..

1) Brain Teaser #1

You have 35 pens, all with equal weight except one (greater or lesser) and you are provided with a balance. .What is the least number of measurements you have to take to find the odd man out?

2) Popular Riddle #1

Little hard to term this as a riddle. Anyway. A family as I know has several children. Each boy in this family has as many sisters as brothers but each girl has twice as many brothers as sisters. How many brothers and sisters are there?

3) Logic Puzzle #1

There are 45 teams contesting in a knockout tournament. If a team looses their match, they get knocked out. What is the least number of matches required between the teams, to decide the winner?

4) Logic puzzle #2

If a clock takes 5 seconds to strike 5, how long will the same clock take to strike 10?

5) Mathematical Teaser #1

You can use the digit 9 exactly thrice. Use any mathematical operation and the result should be 1. What are the possible options?


  1. pranav manaktalaMay 8, 2010 at 7:06 AM

    hey dis is pranav manaktala....and the answer to the first question is 35!! tell me weather i am correct or not!!

  2. Hi,

    How did you reason this out as 35?

  3. 1. least no of east number of measurement is 1. if we have 2 sets of 17 each and measure the weight and are equal then the remaining one is the pen we are looking for

    2. 3 sisters and 4 brothers

    3. 46 Match

    4. 11.25 sec 1+(5/4)*9 Sec

    5. 9^(9-9), (9/9)^9

  4. I got the answer for the question of 35 pens as max 5 weighs... Is it correct?

  5. 1.Least measures under any circumstances is 4
    2.same as harsha
    3.43 matches assuming bye for extra guy
    4.harsha explain pls

  6. @Pramod

    Least no measurement will be 1 if you made 2 groups and are of same weight, then the remaining will be the odd

    For 3: i posted wrong ans it would be 41 matches including byes and everything
    > 1 bye + 22 matches -23 teams left
    > 1 bye + 11 matches - 12 teams left
    > 6 matches - 3 teams left
    > 1 bye to final and 1 match
    > final - 1 match - winner

    total: 41

    4 ans explanation: for 5 bells it takes 5 seconds and time count starts after 1st bell. So 4 more left. then 5 sec for 4 bells... diff betweek each bell will 1.25 secs.
    so for 10 bells.. 1(first one) and 9*1.25 which equals to 11.25 secs