Tech engineers are regarded as some of the smartest people in the world.
But even they have a hard time answering the brain teaser questions a lot of tech companies like to ask during job interviews. We went through Glassdoor to find some of the trickiest questions they get asked, and the best way to answer them.
Q1: How many trailing zeros are in the number 5! (5 factorial)?
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Suggested answers:
Option 1: 5!=120. So there is 1 trailing zero.
Option 2: This sounds like one geared not so much
towards getting the right answer, but getting to it the right way. If
you think a bit and say "one", the interviewer will know you did it the
brute-force way, doing the math. You'd get at the answer faster, and
probably impress them more, if you think instead how many times a ten
will be produced in doing that math, rather than what the actual result
of the math will be.
Q2: You have two light bulbs at a 100-story building. You want to find the floor at which the bulbs will break when dropped. Find the floor using the least number of drops.
Suggested answers:
Option 1: Start moving up in increments of 10
floors and dropping the bulb until it breaks (ie: drop from floor 10, if
it doesn't break, drop from floor 20, etc.). Once the bulb breaks, move
down to the floor before it broke on and start moving up floors in
increments of one until the second bulb breaks. This results in a worst
case scenario of 19 drops.
Option 2: 19 drops is not the best worst-case
scenario... imagine trying floor 16, if it breaks, you try 1 - 15 and
thats 16 tries. If it doesn't break, then try floor 31 and if it breaks,
then try 17 - 30 (so 16 tries, including the try on floor 16). And on
and on (45, 58, 70, 81, 91, 100). If you reach 91, you'll have tried 7
floors so far and if it doesn't break, then there's 9 more tries to get
to 100 (thus 16 in the worst case.)
Q3: If you had 5,623 participants in a tournament, how many games would need to be played to determine the winner?
Asked to: Manager at Amazon
Suggested answers:
Option 1: The interviewer is not looking for the
right answer because there can be many. What he/she is looking for is
your logical approach in solving the answer. So you could start by
probing more is first I would like to understand if 5,623 participants
represent the number of team or individuals. Then ask the next logical
question based on the answer."
Option 2: 5,622. Assuming it is a single
elimination tournament. All teams lose one game except the champs. It's
always # of teams - 1.
Q4: There are 20 different socks of two types in a drawer in
a completely dark room. What is the minimum number of socks you should
grab to ensure you have a matching pair?
Asked to: Software development engineer in test at Web trends
Suggested answer: I'm not a mathematician,
statistician, or highly analytical but if you pick up three socks they
could still be all of same type -- even if the odds are 50%. Odds do not
equal reality. So the only way to 'ensure you have a matching pair' is
to pick up 11 of the 20. This is the only foolproof guaranteed way to
get a pair (in the real world and not the world of odds.)
Q5: If you have a square room with no roof, and you had four flagpoles you had to plant on the walls so that each flagpole touched two walls, how would you do it?
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Suggested answer: The answer was that by planting
them on the corners, each one is touching two walls because each corner
is part of two walls. I wanted to pierce two walls with a pole
horizontally too. They said it was an innovative solution.
Q6: There are 9 balls all of which weigh the same except one, what is the minimum weighings necessary to find the ball weighs more (or less)?
Flickr |
Suggested answer: You could do this with two
weighings assuming its a two pan balance -- (1) place three balls on
each side if they balance out then its the remaining three that has
abnormal ball (2) out of that group, place one ball on each side - if
balances it out, the abnormal ball is the remaining one. If the weighing
in step (1) does not balance out, grab the group of three balls that is
light or heavy and repeat step (2) described above."
Q7: You have 2 pieces of rope, each of which burns from one end to the other in 30 minutes (no matter which end is lit). If different pieces touch, the flame will transfer from one to the other. You cannot assume any rope properties that were not stated. Given only 1 match, can you time 45 minutes?
Business Insider |
Suggested answer: Take one rope (Rope A), place it
down as a circle. Light match and start burning rope A at the tips that
are touching. When the rope completely burns out, 15 minutes will have
passed (since both ends are burning and being consumed at once). Hold
the second rope (Rope B) straight and place one end so that it will
immediately catch fire when the two burning points from (Rope A) finally
touch and are just about to burn out. Thus 15 minutes on Rope A + 30
minutes on Rope B gives you 45 mins.
Make a T. Simple
Q8: In front of you are three light switches. Only one does
anything, and it turns on the light downstairs. From here you can't see
the light, and it makes no sound. You must determine which switch
operates the light, but you can only go check it once. How do you figure
out which switch is for the light?
Flickr |
Suggested answer: Flip any switch you want. Wait
for about 5-10 minutes to let the bulb heat up. Flip that same switch
off, and another one on. Go check the light. If it's off and hot, it was
the first switch, if it's on it was the second and if it's cold and
off, it was the last one.
source:mensxp.com
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