Logic Riddles Case 1-5

Logic riddles are always included as one of the hardest riddles. Sometimes you need to work with numbers to solve it, just similar to math riddles. However, most of the times logic riddle is about problem solving, analyze, and creative thinking.

Try 5 of the best logic riddles below. Don't worry, none of them is a tricky puzzle with silly solution.


Logic Riddle Case 001

There are five men, let's say A, B, C, D, and E. All of them have a dot mark in their forehead. They can't see the dot on their own forehead, but can see the ones on others. The owner of WHITE dot is an honest person and will never lie, while the owner of BLACK dot always tell the lie.

This is the statement from A, B, C, and E:
A: "I see 3 whites and 1 black"
B: "I see 4 black"
C: "I see 3 black and 1 white"
E: "I see 4 white"

What color is the dot on each A, B, C, D, E forehead?

Answer:

A, B, C, and E stated a contradiction statement, so only one of them can said the truth.
We don't know yet where D stands, it's still possible that he has black or white color.
Thus, the maximum possibility of white dots are 2, that is D and 1 of A, B, C, and E.
A and E obviously told the lie, as they said there are 3 and 4 person has white dot, which leave us B and C.
Assuming B is white, then he must be telling the truth that he saw 4 black dots, which makes C a liar. This is an impossible situation, since C saw 3 black and 1 white (C has to be a liar, so there must be more than 1 white, meaning it's impossible B saw 4 blacks).
The only possibility is C told the truth.
So, A, B, E have black dots, while C and D have white dots.

Logic Riddle Case 002

There are four people in an adventure race that need to get across a lake. They have only one small canoe. The rules say that only the slowest person in the canoe can paddle, only one or two can be in the canoe at a time, and they must all cross in the canoe. From practice, they know that:

Annie can paddle across in 1 minute.

Bob can paddle across in 2 minutes.

Charles can paddle across in 5 minutes.

Dan can paddle across in 10 minutes.

How do they get everyone across the river in 17 minutes without breaking the rules?

Answer:

First, Annie and Bob make the crossing (2 minutes), then Annie comes back (1 minute). Next, Charles crosses with Dan (10 minutes), and told Bob to takes the canoe back (2 minutes). Annie and Bob will make the last crossing (2 minutes), which gives the total of 2+1+10+2+2 = 17 minutes.

Logic Riddle Case 003

There are three clay containers. One of them has only pennies from the year 2005 in it, one has only pennies from the year 1975 in it, and the third has an equal number of each. They are labeled "2005," "1975" and "MIXED". However, you know that the labels have been switched, so that NONE of the container is marked correctly. Can you properly label the containers without looking in them, and ONLY pulling ONE coin out from ONE container?

Answer:

Just pull one coin from the container labeled "MIXED" None of the container was labeled correctly, so this surely isn't the mixed container. Thus, if you pulled a 2005 penny, the container labeled "1975" must be the mixed container, and the one labeled "2005" is the 1975 container. This also goes the other way around.

Logic Riddle Case 004

There are three switches downstairs. Each corresponds to one of the three light bulbs in the attic. You can turn the switches on and off and leave them in any position.
How would you identify which switch corresponds to which light bulb, if you are only allowed ONE trip upstairs?

Answer:

Turn two of the light switches on. Wait a while, and then turn one of them off, then quickly enter the attic. One light will be on, one off, and one off but still hot.

Logic Riddle Case 005

An old farmer went on a trip with a fox, a goose and a sack of corn. He came upon a river which he had to cross and found a tiny boat to use to cross the stream. He could only take himself and one other - the fox, the goose, or the corn - at a time. He could not leave the fox alone with the goose or the goose alone with the corn.
How he can cross all of them safely?

Answer:

Take the goose over first and come back. Then take the fox over and bring the goose back. Now leave the goose and take the corn over. The corn should be safe with the fox, and come back alone to get the goose. Take the goose over and the job is done.

Not difficult enough? Just wait until we back with more challenging hard riddles soon.

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