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Interview Question Database

Brainteasers

QUESTION INTENT

The interviewer is testing to see how you react to an absurd and strange problem.

TIPS FOR RESPONDING TO BRAINTEASER Q'S 

The way you understand and approach the solution to this type of unexpected question is translatable to how you work through any problem. For example, if you don’t understand a question or need clarification, don’t be afraid to ask questions. Asking questions shows how you work to thoroughly understand a question and are considering many factors for solution.

Why are manhole covers round?

This type of question may be asked for you to consider the design of an item that you see everyday.

Answer Tips

Answer Tips

Manhole covers are round for safety purposes as it’s the only shape that cannot fall through itself therefore the cover can never accidentally fall down the hole.

You’re in a room with 3 light switches, each of which controls 1 of the 3 light bulbs in the next room. You need to determine which switch controls which bulb. All lights are off , and you can’t see into one room from the other. You can inspect the other room only once. How can you find out which switches are connected to which bulbs?


Answer Tips

Answer Tips

In the room with the 3 switches, label them 1,2, 3 Leave switch 1 off. Turn switch 2 on for ten minutes. Now turn it off and quickly turn on switch 3. Go into the room and inspect… The bulb that is still warm but not lit up is controlled by switch 2. The one that’s currently lit up is switch 3. The last one is switch 1.

You have 8 balls. One of them is defective and weighs less than others. You have a balance to measure balls against each other. In 2 weightings, how do you find the defective one?


Answer Tips

Answer Tips

Let’s label each ball a number from 1 to 8. First, we weigh the balls labelled {1,2,3} on the left and {4,5,6} on the right. There are three scenarios which can arise from this: 1) If the left side is heavier, then we know that one of 1, 2 or 3 is the heavier ball. Weigh {1} on the left and {2} on the right. By doing this, we will know if 1 or 2 is heavier. If they balance out, then 3 is the heavier one. 2) If the right side is heavier, then we know that either 4, 5 or 6 is the heavier ball. Weigh {4} on the left and {5} on the right. By doing this we will know if 4 or 5 is heavier. If they balance out, then 6 is the heavier one. 3) If {1,2,3} and {4,5,6} balance out, then we know either 7 or 8 is the heavier one. Weigh both of them to find out which one is heavier.

Imagine you are standing in front of a mirror and are facing it. Raise your left hand. Raise your right hand. Look at your reflection. When you raise your left hand, your reflection raises what appears to be his right hand. When you tilt your head up, your reflection does too, and does not appear to tilt his/her head down. Why is it that the mirror appears to reverse left and right, but not up and down?


Answer Tips

Answer Tips

Mirrors reverses objects front to back relative to the front of the mirror (i.e. point of view of the observer). The mirror does not reverse left to right or any other directions (such as up, down, north, south, etc) as if you were to turn left or right and point, your reflective will be pointing in the same. 

If the time is 11:50, what is the angle between the two hands of the clock?


Answer Tips

Answer Tips

There are 360 degrees in an hour, 60 minutes in an hour and, therefore 6 degrees in a minute. There are 30 degrees between the hour markers on a clock face, therefore, the hour hand moves at the rate of 30 degrees per hour. At ten to the hour, the hour hand will have completed five sixths of its 30 degree journey [30x5/6 = 25. Therefore, when the minute hand rests on the '10' at 11:50 the interior angle between the two hands is 55 degrees. Notice I said 'interior' angle because someone will always point out that you didn't specify it in the question and show off by asking for clarification or giving both answers. The exterior angle is 305 degrees between the two hands, in that case. 

How would you describe a specific mathematical process/coding language/science system to a child?


Answer Tips

Answer Tips

Break down your knowledge of the topic into its core concepts and use the simplest language to explain it. 

There are 3 baskets. One basket contains apples, the other basket contains oranges only and the last basket contains a mixture of apples and oranges. Each basket is closed and is labeled with ‘Apples’, ‘Oranges’ and ‘Apples and Oranges’. However, each of these labels is always placed incorrectly. How would you pick only one fruit from a basket to place the labels correctly on all the baskets?


Answer Tips

Answer Tips

Say you pick a fruit from the basket labeled 'Apples and Oranges'. If the fruit you chose was an apple, then we know the label is incorrect and this basket contains only apples. If you check the basket labeled 'Oranges', we know that the basket either contains oranges or apples and oranges'. Since we have established the first basket (labelled 'Apples and Orange') contained apples, we know the basket labeled 'Oranges' contains both apples and oranges. From deduction, we know the basket labeled 'Apples' contains only oranges. The same can be applied if an orange was chosen from the first basket. 

How would you test a calculator?


Answer Tips

Answer Tips

Testing can be divided into two broad categories of function and non-functional testing. Explain both test cases for both types of testing. For example some test cases would be to check if division by zero, check BEDMAS for the order of operations and/or if the clear button clears the screen to 0.