Interview Puzzles Set 11 – Maximum Distance Travelled | The Fake Note | Colliding Ants

If you correct your mind, the rest of your life will fall into place.

– Lao Tzu

Algorithmic thinking is really important as it enhances your thinking skills and can be nurtured with practice. (Refer the previous tutorial to know more about Algorithmic Thinking and try the puzzles before moving on to the solutions.)


 Solutions for the previous problems

Puzzle 10.1 Solution – Identify The Identical Sisters

Correct Answer:  The girl on the left is Sally, the girl in the middle is Sue and the girl on the right is Sarah.

Explanation: The girl on the left said that the one in the middle is Sarah, then definitely the girl on the left can’t be Sarah because if she was Sarah she wouldn’t say a lie. For the same reason, the girl in the middle can’t be Sarah. Therefore, the girl on the right is Sarah and since she told that the girl in the middle is Sue, it would be true because she never lies. Thus, the girl on the left will be Sally.


Puzzle 10.2 Solution – The Missing Fish

Correct Answer:  There were only three people- the son, his father, and his grandfather.

Explanation: Since there were only three fishes and none of the fish were eaten, lost, or thrown back, there must be only three people. The three people would be a son(A), his father(B), and his grandfather(C). The two fathers would be B and C where as the two sons would be A and B(B is the son of C).


Solving these puzzles is fun, isn’t it? So, wear your logic caps and get ready for your next brain workout:

Algorithmic Thinking
Algorithmic Thinking

Quiz 11.1  – Maximum Distance Travelled

A car needs 4 tyres but we have 5 tyres(1 spare tyre). Each tyre wears off after travelling a maximum distance of 20000 miles. What is the maximum distance the car can travel before any two tyres wear off?

You are allowed to change tyres (using the spare tyre) unlimited number of times.

Just think about it and post your answer in the comments. I’ll explain this in the next tutorial.

Solution Added – Solution of “Maximum distance travelled” puzzle


Quiz 11.2 – The Fake Note

A Lady bought an item of Rs.500 from a Shopkeeper. She paid him through a Rs.2000 Note. Since the shopkeeper did not have any change, he asked his friend(neighbouring shopkeeper) to give him change for that Rs.2000 note and paid Rs.1,500 back to the Lady.

After a few days, the second shopkeeper realized that the note was fake, so he went to the first shopkeeper and took his Rs.2000 back from him.

The first shopkeeper kept thinking about his loss but couldn’t figure out how much money he lost in total. Can you figure it out for him?

Just think about it and post your answer in the comments.

Solution Added – Solution of “The Fake note” puzzle


Quiz 11.3  – Colliding Ants

Three ants are resting on the three vertices of a triangle. After some time, all three ants start moving along the edges of the triangle. Can you find out the probability that any two ants will collide?

Just think about it and post your answer in the comments. I’ll explain this in the next tutorial.

Solution Added – Solution of “The Colliding Ants” puzzle


So start thinking and comment answer to the questions asked above and wait for the next post for the solutions.
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Keep Learning. Happy Learning 🙂 

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