Although you probably won’t be given a Rubik’s Cube to solve during your hedge fund job interview, you should be ready to solve a puzzle of some sort. Make sure you think through the question before jumping into an answer. And, for goodness’ sake, answer the question that is asked! Nothing decreases your chance of getting a job you are qualified to do faster than not answering the right question.
Q: Picture a 10x10x10 “macro-cube” on the table. This big cube is made up of 1x1x1 “micro-cubes”. Your dog walks by and knocks the macro cube off with his tail, causing it to crash to the ground. When it hits, the impact causes the entire outer layer of micro-cubes to fall off. How many micro-cubes are on the floor?
A: First, don’t beat the dog, he was just happy to see you. This is a popular question and you should be ready for it. There are a couple ways to solve this. The first (not the best), is to count the number of cubes on each face and add them up. This math is confusing for most people.
The better solution is to focus on the structure of the problem. The original macro-cube and new smaller macro-cube hold the answer. The difference between their volumes is how many micro-cubes fell off. The volume of a cube is n cubed. The answer is, therefore, 10 cubed – 8 cubed. So, 1,000 – 512 = 488.
Note: A common mistake is for people to think because only one layer fell off, the solution is 10 cubed – 9 cubed.
Special thanks for this interview question to Timothy Crack, author of Heard on the Street: Quantitative Questions from Wall Street Job Interviews
Rubik’s Cube: A question, waiting to be answered
2 Answers 2 Sorted by:
The obvious answer would be $6times 10times 10=600$ since each face of the cube has $10times 10$ “sides” on it and there are 6 faces of a cube.
However, if this one of those silly “lateral thinking” questions, perhaps the paint seeps between the “cracks” and in fact every “side” of each of the $10times 10times 10=1000$ “minicubes” making up a Rubiks-style cube is covered, so that therefore there are $6000$ “sides” painted black.
The actual question asked MAY have been: if you drop a $10 times 10 times 10$ cube into a bucket of black paint, how many “cubies” have AT LEAST one side with black paint on it.
In this case, there is an $8 times 8 times 8$ cube in the middle that hasnt been touched. So the answer is $10^3 – 8^3 = 488$.
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A couple had to take shelter in a hotel for they could not proceed their journey in the rain. Having nothing to do at all, they started playing cards. Suddenly there was a short circuit and the lights went off. The husband inverted the position of 15 cards in the deck (52 cards normal deck) and shuffled the deck. Now he asked his wife to divide the deck into two different piles which may not be equal but both of them should have equal number of cards facing up. There was no source of light in the room and the wife was unable to see the cards. For a certain amount of time, she thought and then divided the cards in two piles. To the husbandââ¬â¢s astonishment, both of the piles had equal number of cards facing up. How did she do it?
Difficulty Popularity Below rebus represents the current Temperature. 0 ========= B.Sc LLB What is the current Temperature ?
Difficulty Popularity Aamir has a cube with 4 inch side. He paints it red, green and black on the opposite faces. After that, he cuts it into one inch cubes. Answer the following questions (1-4) relating them with the once inch cubes. Q1. How many cubes are left with only one face painted? a) 8 b) 16 c) 24 d) 32 Q2. How many cubes have two of their faces painted? a) 8 b) 16 c) 24 d) 32 Q3. How many cubes have four faces painted? a) 0 b) 4 c) 8 d) 12 Q4. How many cubes are left with none of their faces painted? a) 0 b) 4 c) 8 d) 12
Fifteen Minutes. After frying for five minutes, you can take out one steak and put the third one inside while turning the other one inside. After five more minutes, one steak is fried from both sides and you can take it out. Now put in the steak that we removed and turn the other one inside. After five more minutes, they both will also be fried from both sides.
Difficulty Popularity There are 100 doors. 100 strangers have been gathered in the adjacent room. The first one goes and opens every door. The second one goes and shuts down all the even numbered doors ââ¬â second, fourth, sixth… and so on. The third one goes and reverses the current position of every third door (third, sixth, ninthââ¬Â¦ and so on.) i.e. if the door is open, he shuts it and if the door is shut, he switches opens it. All the 100 strangers progresses in the similar fashion. After the last person has done what he wanted, which doors will be left open and which ones will be shut at the end?
Special thanks for this interview question to Timothy Crack, author of Heard on the Street: Quantitative Questions from Wall Street Job Interviews
Although you probably won’t be given a Rubik’s Cube to solve during your hedge fund job interview, you should be ready to solve a puzzle of some sort. Make sure you think through the question before jumping into an answer. And, for goodness’ sake, answer the question that is asked! Nothing decreases your chance of getting a job you are qualified to do faster than not answering the right question.
A: First, don’t beat the dog, he was just happy to see you. This is a popular question and you should be ready for it. There are a couple ways to solve this. The first (not the best), is to count the number of cubes on each face and add them up. This math is confusing for most people.
The better solution is to focus on the structure of the problem. The original macro-cube and new smaller macro-cube hold the answer. The difference between their volumes is how many micro-cubes fell off. The volume of a cube is n cubed. The answer is, therefore, 10 cubed – 8 cubed. So, 1,000 – 512 = 488.
Note: A common mistake is for people to think because only one layer fell off, the solution is 10 cubed – 9 cubed.
FAQ
What is the logic of Rubik’s cube?
- Focus & Concentration. Solving the cube requires a lot of concentration to solve and when your brain focuses on this one task it increases your concentration. …
- Perseverance. The cube requires immense perseverance. …
- Memory. …
- Reflexes. …
- Problem-Solving Skills. …
- Mindfulness.
Which method is fastest in Rubik’s cube?
What are the basics of a Rubik’s cube?
