Critical Thinking Questions – The Thought Process Behind Answering the Questions (Part 02)

This is a continuation of Critical Thinking Questions and Evaluations - Part 01, bringing with it some new questions!

Question 4: Wanted Poster

Question:Sam Slug was standing in the post office looking at a 'wanted' poster. Someone asked him who the main in the poster was and Sam replied, “Brothers and sisters I have none, but this man's father is my father's son.” Whose picture was on the poster that Sam was looking at?

Thought Process

Since we are dealing with family relationships here, we are evaluating the relationship of the person in the picture to Sam Slug. First off, we have this information:

  • He has no brothers and sisters. This does not really help all that much, but let us take a look at the next part
  • This man's father is his father's son

Okay, so we start by considering that Sam Slug is a male (as the question even refers to him as a “him”). “This man's father is my father's son” leads us to believe that because Sam Slug has no brothers, he must be the father of whoever is in the image. This would mean that it has to be his son.


Sam Slug was looking at a picture of his son. The puzzle of the statement “this man's father is my father's son” is easily solved if the word “me” is substituted for “my father's son.” the statement then reads, “Brothers and sisters I have none, but this man's father is me.”

Question 5: Speed Shopping

Question: Mr. Greenwich and his wife were shopping when they decided to go their separate ways to speed things up. They agreed to meet at the bank at 2:00 pm. Mr. Greenwich realized several minutes later that he had forgotten his watch. He asked a lady walking by for the correct time. Her watch was five minutes fast, but she thought it was ten minutes slow. Mrs. Greenwich had also forgotten her watch so she asked a gentleman passing by for the correct time. The man's watch was ten minutes slow, but he thought it was 15 minutes fast. Taking into account the errors in the watches, who was at the bank first and at what time did they arrive?

Thought Process

In a sense, this is a bit of a mathematical equation. Let us start with Mr. Greenwich and his situation. The person he asked for the time from had her watch five minutes fast, but she thought it was ten minutes slow. Let us break it down like this:

  • 5 minutes fast = +5
  • 10 minutes slow = +10

This means that the time she gave was 15 minutes off. Being that the time was slow, we can then go in the forward direction (meaning that what ever time she gave was 15 minutes ahead of where it should have been). So essentially Mr. Greenwich is 15 minutes ahead.

For Mrs. Greenwich, we can break it down in a similar method, as such:

  • 15 minutes fast = -15
  • 10 minutes slow = -10

Being that the real time was ahead of the watch, and the man gave the time based on it being ahead, we can point both of these in the negative direction and state that Mrs. Greenwich will be there 25 minutes late.

Taking these times in to consideration and looking at their meeting time of 2:00 pm, we can tell that Mr. Greenwich will be there at 1:45 pm (being that he is 15 minutes ahead) and his wife will be there at 2:25 (since she is 25 minutes behind schedule). This also means that Mr. Greenwich will end up waiting for his wife for 40 minutes, despite both of them thinking that they were on time!

Editor's Note: This is a very tricky mind puzzle because you need to really think about what is being said and how it correlates to the times. It is easy enough to get it backwards and think that the man got to the bank late and the woman arrived there early. Critical thinking at its finest!


Mr. Greenwich arrived first at a quarter until two. He was told a time that was actually 15 minutes faster than the true time. Mrs. Greenwich arrived at twenty five after since she was told a time that was 25 minutes slower than the true time.

Question 6: Granny Smith's Train

Question: Granny Smith boarded the last car of a passenger train to find every seat occupied. She set her luggage down just as the train was passing the 'Soul-Ace Hotel.' Granny walked forward through the train at the steady speed of 1.5 kph. A half hour later, Granny reached the front of the train. Still unable to find a seat, she headed back to her luggage, walking at the same speed as before. When she reached her luggage, they were passing City Hall, which is ten kilometers from the 'Soul-Ace Hotel.' How fast was the train moving?

Thought Process

This question is probably a lot easier than you may think, because it gives a lot of details that really are not needed. If you scan through it real quick, you may be able to figure this one out pretty quick, and there is no math involved! It breaks down like this:

  • Granny Smith walked to the front of the train at 1.5 kph, which took her half an hour
  • She then walked back to where she started, still at 1.5 kph, which took another half hour (we know this because it took her a half hour to get to the front, and if she was moving at the same speed the entire time it would take the same amount of time)

From this, we see that Granny walked for an entire hour. Her speed here is actually completely irrelevant; it has no impact on the result. All we needed to know was the time.

We then see that when she got back to the back of the train, it had gone a total of 10 km. Being that this is ten kilometers, and we know that the train was going for a period of an hour, we know that it was going at a speed of 10 kph. Easy!

Editor's Note: This is one of the questions where it is really easy to get caught up in details that just do not matter. Always read the question thoroughly and try to pick out what you are going for, and use that to determine what else is needed in order to solve it. By doing this, you could tell pretty quick what the answer to this was going to be!


The train was moving ten kph. The speed at which Granny walked through the train is of no consequence. All we need to know is the elapsed time. Granny took one hour to make the round trip and during that time the luggage traveled ten kilometers.


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