Tech engineers are some of the smartest multitude in the public .
But even they have a hard time answering the brain annoyer interrogative a luck of tech companies wish to take during business consultation .
We move through Glassdoor to find some of the trickiest head teaser questions they get asked , and the respectable way to respond them .
Systems engine driver at Google : " How many trailing aught are in the turn 5 ! ( 5 factorial ) ? "
Suggestedanswers :
" 5!=120 . So there is 1 trailing zero . "
" This sounds like one pitch not so much towards getting the correct result , but getting to it the right way . If you call up a scrap and say " one " , the interviewer will know you did it the brute - force direction , doing the math . You ’d get at the answer quicker , and probably impress them more , if you think rather how many sentence a ten will be produced in doing that mathematics , rather than what the actual answer of the mathematics will be . "
Software engineer at Facebook : “ You have two lightbulbs at a 100 - story building . You want to discover the base at which the bulbs will break up when dropped . observe the floor using the least issue of drop . ”
" Start moving up in increments of 10 floor and dropping the light bulb until it cave in ( ie : drop curtain from floor 10 , if it does n’t burst , set down from floor 20 , etc . ) . Once the bulb breaks , move down to the floor before it broke on and start proceed up floors in increments of one until the second bulb time out . This results in a worst case scenario of 19 fall . "
" 19 drops is not the best bad case scenario … imagine trying level 16 , if it breaks , you try on 1 - 15 and that s 16 tries . If it does n’t soften , then try out floor 31 and if it breaks , then try 17 - 30 ( so 16 endeavor , including the attempt on storey 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 does n’t smash , then there ’s 9 more tries to get to 100 ( thus 16 in the bad typesetter’s case ) . "
Manager at Amazon : “ If you had 5,623 participants in a tourney , how many game would need to be played to determine the winner ? ”
" The interviewer is not look for the right answer because there can be many . What he / she is looking for is your lucid approach in solving the answer . So you could start by poke into more is first I would like to understand if 5,623 participants stage the number of team or individuals . Then ask the next logical question base on the resolution . "
" 5,622 . Assuming it is a single elimination tourney . All teams mislay one game except the champ . It ’s always # of teams - 1 . "
Software Development Engineer in Test at Webtrends : " There are 20 dissimilar socks of two type in a drawer in a altogether dark-skinned room . What is the minimum telephone number of wind cone you should grab to see to it you have a twin pair ? "
Suggestedanswer :
" I ’m not a mathematician , statistician , or extremely analytic but if you pick up 3 air sock they could still be all the same case - even if the betting odds are 50 % . betting odds do not rival reality . So the only way to ' see you have a matching pair ' is to break up up 11 of the 20 . This is the only fool proof warrant manner to get a pair ( in the real world and not the world of betting odds ) . "
entanglement Technology Intern at Riot Games : “ Imagine that you have three box , one containing two black wits , one containing two lily-white marbles , and the third , one ignominious marble and one blanched marble . The box were labeled for their contents - BB , WW , BW - but someone has alternate the labels so that every box is now wrongly label . You are allowed to take one marble at a time out of any box , without looking deep down , and by this process ofsamplingyou are to see the subject matter of all three boxes . What is the minuscule figure of lottery need to do this ? ”
" The key affair here is that the box does not contain what it says on the label . As such you could assure the contents of each box with one draw . Here ’s how : Draw a marble from the box labeled BW ( since it is labeled BW it must be either BB or WW ) If you draw a Edward White for example you know 100 % that it is the WW corner . Then there are only two box left labeled WW and BB in this exemplar and the only two things that they can be are BB or BW . The box labeled BB can not be BB and so hence must be the BW . This leaves the box labeled WW to be BB by elimination . Same thing works if you pick a fatal marble first . The key fruit is picking from the BW loge in the showtime and confirming what it in reality is . One draw is the smallest bit needed . "
Software Engineer at Cisco : " If you have a hearty room with no roof , and you had four flagpoles you had to plant on the bulwark so that each flagstaff touch two walls , how would you do it ? "
" The solution was that by planting them on the corner , each one is touching two wall because each niche is part of two rampart . I wanted to thrust two walls with a rod horizontally too . They said it was an innovative solution . "
software system technologist at D. E. Shaw & Co. : " Given 9 balls all of which weigh the same except for one , what is the lower limit of weighings necessary to find the nut press more ( or less ) ? "
" You could do this with two advisement take on its a two cooking pan balance - ( 1 ) place three balls on each side - if they balance out then its the stay three that has abnormal ball ( 2 ) out of that group , place one ball on each side - if balances it out , the abnormal formal 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 whole step ( 2 ) described above . "
ASIC Verification applied scientist at Zoran : " You have 2 while of rope , each of which cauterize from one end to the other in 30 bit ( no matter which closing is lit ) . If unlike musical composition touch , the flame will transfer from one to the other . you may not assume any rope properties that were not tell . Given only 1 match , can you clock 45 minutes ? "
" Take one rope ( Rope A ) , place it down as a circle . Light match and commence burn forget me drug A at the tips that are affecting . When the rope completely burns out , 15 minutes will have passed ( since both end are burn and being consumed at once ) . contain the second roofy ( Rope B ) flat and place one destruction so that it will immediately catch fervor when the two burn points from ( Rope A ) finally touch and are just about to burn out . Thus 15 minutes on Rope A + 30 minutes on Rope B give you 45 mins . "
" Make a T. Simple . "
Software railroad engineer at Raytheon : " In front of you are three light switches . Only one does anything , and it turns on the light below . From here you ca n’t see the light , and it seduce no speech sound . You must determine which switch operates the brightness level , BUT you may only go check it once . How do you figure out which switch is for the light ? "
" Flip any switch you want . Wait for about 5 - 10 minutes to let the light bulb heat up up . thumb that same switching off , and another one on . Go check the light . If it ’s off and hot , it was the first permutation , if it ’s on it was the 2nd and if it ’s cold and off , it was the last one . "
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