Going for a job interview is nerve-racking at the best of times, but tech giant Google has become notorious for asking fiendishly tough questions.

The company used to ask head-scratching questions such as 'How many piano tuners are there in the world?' and 'How many golf balls does it take to fill a school bus?'

But some of the riddles were so tough they have now been banned from the interview process.

One of the tough teasers that candidates used to be asked was: 'How many piano tuners are there in the entire world?'

The riddle is known as a Fermi problem, named after the physicist Enrico Fermi who was known for his ability to make good calculations with very little information or even none.

Its purpose is to test a candidates approximation skills as well as their ability at dimensional analysis.

The puzzle is solved by multiplying a series of estimates to get to the right answer. So a candidate would have to estimate factors such as how many households have a piano, how often they are tuned to figure out how many piano tunings take place a year.

They then need to calculate the average working hours of a piano tuners and the number of jobs they carry out.

The number of piano tunings that take place per year divided by the number per year per piano tuner should yield the answer.

Google candidates going for a role as product manager also used to be asked: 'How many golf balls can fit in a school bus?

To solve it one must calculate the volume of the average golf ball and the volume of the average school bus, taking into account factors like the seats and other fixtures taking up space.

The answer is the volume of the bus, divided by the volume of the balls.

As well as questions involving calculation and physics, Google used to ask would-be employees to solve logic puzzles.

One of the riddles was: 'Every man in a village of 100 married couples has cheated on his wife.

'Every wife in the village instantly knows when a man other than her husband has cheated but does not know when her own husband has.
“村子里的每位妻子都能立即知道别人的丈夫有不忠诚的行为，但当自己丈夫不忠诚时却浑然不知。”

'The village has a law that does not allow for adultery. Any wife who can prove that her husband is unfaithful must kill him that very day. “
”村子里有规定，不允许任何通奸行为。任何一位能证明自己丈夫不忠的妻子必须当天就把他杀了。”

'The women of the village would never disobey this law. One day, the queen of the village visits and announces that at least one husband has been unfaithful. What happens?'
“村子里的女人绝不敢违法规定。有一天，村里的女头领出来视察环境并宣布：村子里至少有一个丈夫出过轨。然后会发生什么事？”

Although opinion varies as to the correct answer, a popular solution is to assume that all the cheating husbands will be executed 100 days after the queen's announcement.

Every wife in the village instantly knows when a man other than her husband has cheated, so if there's only one unfaithful man she will know it's her husband and will kill him that day.

Bearing in mind that the queen has said that at least one man has cheated, there could be more than a single adulterer.

If there are two cheaters, 98 women will know who they are. The next day when the wives who have been cheated on see that nobody has been executed they will realise the only explanation is that their husbands are the culprits, and will kill them.

By that logic, 100 cheating husbands will be executed on the 100th day, as the riddle states that every man in the village has cheated on his wife.

A riddle about pirates sounds complicated but the answer is in fact quite simple.

You’re the captain of a pirate ship, and your crew gets to vote on how the gold is divided up.

'If fewer than half of the pirates agree with you, you die. How do you recommend apportioning the gold in such a way that you get a good share of the booty, but still survive?
”如果少于半数的人支持你，你就得死。所以你会怎么建议把金子分配得自己既能获得很好的收益，还能幸免于难呢？”

The solution is to share 51 per cent of the treasure.

Another logic puzzled candidates were given to solve was: 'How many times a day do the hands of a clock overlap?'

The hands overlap once an hour, but 11 times in 12 hours and 22 times in a day. This is because the overlap at 12 has already been accounted for. The overlaps occur at 12, 1.05, 2.11, 3:16, 4:22, 5:27, 6:33, 7:38, 8:44, 9:49 and 10:55 in the morning and after midday at 12, 1.05, 2:11, 3:16, 4:22, 5:27, 6:33, 7:38, 8:44, 9:49 and 10:55.

9 OF GOOGLE'S TOUGHEST BANNED QUESTIONS

1.You have to get from point A to point B. You don’t know if you can get there. What would you do?
1. 你必须从A点走到B点，但你不知道你能不能达到那里，你会怎么做？

2.You are shrunk to the height of a nickel and your mass is proportionally reduced so as to maintain your original density. You are then thrown into an empty glass blender. The blades will start moving in 60 seconds. What do you do?
2. 你的身高被缩至硬币大小，你的体重也相应按比例减少到维持身体的原始密度。然后你被扔进了一个空的玻璃搅拌器，搅拌刀片将在60秒后开始转动。你会怎么做？

3.Imagine you have a closet full of shirts. It’s very hard to find a shirt. So what can you do to organize your shirts for easy retrieval?
3.想象你有一个装满衬衫的柜子。你很难找到一件合适的衬衫。因此你如何整理这些衬衫以便寻找？

4.Explain the significance of 'dead beef'

5.How much should you charge to wash all the windows in Seattle?
5.把西雅图所有的窗子都洗一遍要花多少钱？

6.If you look at a clock and the time is 3:15, what is the angle between the hour and the minute hands?
6.如果你看了一下钟表，时间显示3：15，那么时针与分针之间的夹角是多少？

7.What is the probability of breaking a stick into 3 pieces and forming a triangle?
7.把一根棍子折成3份刚好能拼成一个三角形的几率是多少？

8.What method would you use to look up a word in a dictionary?
8.你会采用什么方法在字典里查找一个单词？

9.A man pushed his car to a hotel and lost his fortune. What happened?
9. 一个男人把车推到酒店里却把财产丢了。发生了什么事？