Interesting Puzzles

Interesting brain teasers, logical puzzles, mental riddles, all in one place with answers.

Puzzle #22 – Distance Puzzle


We solved this puzzle by pythagoras theorem. Thus the answer is 5 Km.

Puzzle #21 – Arithmetic Puzzle

The Answers are
A =-25 ,7, 11 , 6 , 12 , 14 , 8, 9
B =-36 , -4 , 0 , -5, -1 , 13, -3 , -2
C = 37 , 5 , 1 , 6 , 0 , -2 , 4 , 3
D = 34 , 2 , -2 , 3 , -3, -5 , 1, 0

Puzzle #20 – Fruit Puzzle

Answer is 33.
Apple is 7.
Group of grapes is 12. (5 + 7).
Bananas are 6 (7= 6 + 1) so, the value of each banana is 2.
So 7 + 24(2 groups of grapes) + 2(single banana) = 33.

Puzzle #19 – Lock Puzzle

The code is 718
From Clues 1 and 2 we know that one 5 is not in the code
from Clue 3 we know that 1 and 7 are part of code
from Clue 4 we know that 8 is also in the code.
So the 3 numbers in the code are 8,1 and 7. Now solve for order.
From Clue 1 we know that 8 is the third number
From clue 3 we know that 1 and 7 are in wrong place so we now know that,
7 is first, 1 is second in code and 8 is third.
So the Code is 718.

Puzzle #18 – Puzzle of 3s

Answer is -7.

Many think it is 1 because of one of two common errors. The first common error is failing to see that when a number is alone inside a set of parentheses, you remove the parentheses. If a number is sitting beside a set of parentheses with only a number inside them, it’s multiplication. The second common error is believing multiplication always comes before division. That isn’t true. They hold equal priority and are performed in order from left to right. This holds true for addition and subtraction and they are also performed in order left to right.


With a fraction, we perform the top and then the bottom.


Divide by the bottom number of 3.


Congratulations if you put -7.

I’m sure some won’t believe me and will say there can be two answers or that’s not how they used to teach it or this is crazy new common core method, but it’s not. Perhaps you were taught incorrectly, but the order of operations has never changed. The oldest algebra I have researched and found was printed in 1910, and it is used in it this way. Unless you went through school before 1910, this is the method that should have been taught.

This question and answer was submitted by one of our facebook readers – Eric Peyton, who is a high school math teacher. So credit goes to him for this wonderful question.

Puzzle #17 – Tank Puzzle 2

Tank #2 will only start filling up if and when tank #1 fills to the top, before which tank #3 will start filling up. Tank #6 won’t fill up because #3->#6 is blocked. So tank #5 will start filling up. Tank#5->#10 is blocked. So 8 will start filling up because #9, #11 & #12 all three are blocked at the point of split between three.

Puzzle #16 – Paper Puzzle

Answer is B.

Puzzle #15 – Color Blindness Test


Puzzle #14 – Circles Puzzle

Answer is 20.

Puzzle #13 – Arithmetic Puzzle

The answer is -31.
The value of 6 spoked wheel is 6.
The value of 10 forked tree is 10.
The value of 4 leaved clover is 4.

So no matter what you follow PEMDAS or BODMAS, the equation should be solved in the following order: multiplication, addition, subraction.

Therefore the final equation becomes 5 – 4 x 12 + 12 (wheel is 5 spoked here, clover is four leaved and the tree is 12 forked). So according to original order of operations it should be solved as follows:
5 – (4 x 12) + 12
5 – 48 + 12
-43 + 12 (Addition & Subtraction have equal precedence in order operations and should be solved from left to right).

Therefore the answer is negative 31 or -31.

12. 13524? Puzzle

The answer is ‘R’. It represents the gear stick. The number 1-5 represents gears and the last one thus should be reverse i.e. R.

11. Matchstick 508 Puzzle

Answer is 51181 (Fifty one thousand one hudred and eighty one). Remove top and bottom matches from the zero in 508 and create the number 1 after eight. So zero becomes 11 and the whole number becomes 51181.I am seeing people are getting really creative on our facebook post, giving really creative answers. One of them said 511811, which can be achieved by removing two matchsticks from 0 and using them to create 11 after the 8, but you would end up with two ones which look dwarfed compared to other numbers. One answer which I can really get behind is 5^118, which would end up creating an 83 digit monstrosity. Is this the right answer? It is up for the audience to decide in the comments. If you can come up with an even bigger number, let us know.

10. How many of these Brain Teasers can you solve?

1. Top Secret.
2. Back in 5 Minutes.
3. Hole in one.
4. Walking on Thin Ice.
5. You’re Under Arrest.
6. Broken Promise.
7. Empire Strikes Back.
8. Reading Between the Lines
9. Life After Death.

9. What will be the next number?

The answer is the 44. Column1: [(7×4)+1]-11=18. Column2: [(8×5)+2]-12=30. Column3:

Logical Puzzle

Jonathan Chaim. Geniuses Only. Look Closely on details. Reshare to see your friends. Banana Clock Shapes Puzzle

The answers is 38. The figures represent 15, also notice that the sum of all their sides is 15 (6+5+4). The four bananas represent 4. Clock face with 3 o’clock represents 3. Therefore 2 + 3 + 3 x 11 (clock face with 2 o’clock, three bananas, 11 sided figure) equals 38. According to Mathematic BODMAS rule, numbers in such sequence should be multipled before addition.

Cube Puzzle

The answer is C.
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Which tank will fill up first?

The tank F will fill up first. D, E & G will never fill up because the input pipe for D is blocked. So C will start filling J. I will only start filling up if & when J fills up, before which L will start filling up. The water from L flows into pipes leading to F & H, but H won’t fill up because it’s input pipe is blocked. Therefore F tank will fill up first.
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  1. You can’t answer the logical puzzle where there is no way to equate the 2 o’clock clock and 2 5 pointed stars. You can assume that they are worth a value but there is no way to definitively say that this is the correct value as there is no equation to prove them against

    • If the six pointed star equals 6, the four bladed fan equals 4, and the three bladed fan equals three then logic say a five pointed star is equal to five. If the clock that reads three is equal to three then logic would say the clock that reads two is equal to two.

    • Thank you, Alan! I agree with your analysis. I have seen similar questions around the Internet. I very seldom see your answer put forth. Although I have tried to point out the fallacy would give way to this:
      X + X = 8
      X + Y = ?
      ? = 7 as ‘X’ has four legs and ‘Y’ has three legs, or ? = 9 because of the order of the alphabet. High School and College mathematics teachers beware. There are minions scheming to undo your work!

  2. Which tank fills up first Qs.. Depending on the rate of water that is being poured into A. As if you dump a large amount of water in A at once it will be the first one full. But if the rate of flow is slow then the answer will be F.

          • Due to atmospheric pressure working against gravity, there would be significant resistance to the water moving into Tank F. You would find that Tank L would start backing up as well, to be roughly equal to the amount in Tank F. However, this atmospheric pressure is not an issue for water moving from Tank J to Tank I, as the atmospheric pressure in the pipe connecting the two is much less than the forces of gravity and atmospheric pressure in Tank J. This is enough to force water up the pipe to start overflowing into Tank I. It only needs to get higger than the brim of the pipe before gravity works to take it into Tank I. From there the qater will drain into Tank K, long before any overflow into Tank L would cause the levels in either Tank L or Tank F to reach the point of overflowing as described above.

          • It isn’t G Mark, because to get to G, the water must first pass through D. And the pipe leading from C to D is blocked. Therefore, you wouldn’t be able to get the water to flow to G.

          • Because F is not only subject to gravitational force and atmospheric pressure greater than all other buckets, F is also at the lowest height from all others.

    • in the answer it states that, i will only fill up when j fills up, but before that would happen l would start filling up. ( i think this is because for the water to truvel up a pipe, the previous tank must be full to get the pressure?) so with that in mind, before F can start filling up surely L must be filled up first and the pipe below that eventually feeds tank F as again, the water has to travel upwards to fill tank F?

  3. In triangle puzzle, as in all Geometry, rather than drawing or coloring each triangle, just letter each intersecting point then just list all by letter (e.g. ABC, ABD, ABE, AFG, AFH, AFE, etc)

  4. With the water tanks, you forget to take into fluid pressure – the amount of water over a larger surface area in Tank J means that the water would reach higher up the reduced surface area of the pipe to I BEFORE the overflow to L is necessarily reached, and thus I may fill up and drain to K BEFORE the system from L is even reached…

    • Water fills evenly in a system, so whichever is the lowest will fill first. Assuming that these are all open tanks, as shown in the picture, it will be the only one that fills. Once the water fills F it will begin overflowing and no other tanks will be filled.

    • Er, actually no. The water in the adjacent pipes will always be the same level as in the main tank, assuming that they are all open to atmospheric pressure.
      The surface areas of tank and pipes is completely irrelevant. The only pressure in the water is the hydrostatic pressure which is determined by the local depth of the water only, assuming static conditions.
      Therefore F will fill first.

      • A larger surface area means more pressure – it also tends to mean a larger volume (given the same depth) which means more gravity affecting it. So how about YOU go back to school?

      • Hi CF. Pressure is inversely proportional to area or volume. Taking that into consideration among other factors, F would get filled up first.

  5. i’d like to challenge the creator of this puzzle and say that F is not the right answer according to my theory and how the question is worded…

    i know this answer will be the most controversial, but the “Fill Up” answer is A.

    if they meant to say “Which Tank Will Spill Over or Fill Up To The Brim”, then yes… F.

    but the fill up is only up to the point of what the “tank” can hold. any wall that is built past that “hold” point is just part of the illusion.

    • Tank fill:
      1. Depends on your definition of ‘fill’. Is it full when it reaches the pipe and can go no higher or when it reaches the top of the tank?
      2. If you define it as the top of the tank, then there are two possible answers – A or F – which depends on whether A drains faster than it fills.

    • When something is full, it has reached its maximum capacity. You are arguing “Fill Up” and “Fill Up To The Brim”? Come on, that’s like arguing “Slap Me” and “Slap Me In The Face”, you know exactly what is meant. How can A reach its maximum capacity first? As it is in the process of “FILLING UP” (please note, it is NOT full at this point) it starts feeding tank B.

      No need to get technical with wording… It’s Tank F Gil.

    • So if A has filled to its “Maximum Capacity” as you say, what would we call it once all the other tanks are filled, then A finally fills to the brim? Would this mean A has filled to more than its Maximum Capacity? No Such.

  6. On the puzzle of: Which Tank will fill up first? I believe the answer is incorrect. Why Would it not be K? I the J tank once it’s starts to fill, once it passes the first tube it will automatically start to fill the tube as well and slow the process of filling the tank. By the time the tank is filled the first tube will have already started to drain into I which is draining into K and filling K. Once K is about 1/8-1/4 full, F should have started to fill.(that is a lot of water to fill the tube before it Starts to Fill F)

  7. L. Water isnt going to magically fill F when its fed from the bottom. Which means no matter how you set it up L would have to be full before F can be. You’re pushing water up into a container using gravity. If you had two identical containers that are connected at the bottom and started filling one, the displaced water would fill both and the water will level out. They both couldnt be full at the same time unless the one being filled is full first. Jeez its not that hard. Bad fail here

  8. I disagree with the answer to which tank will fill up first. Since the illustration shows water flow as “drips” Tank L would be fill up first because the pipe leading to tank F is going upstream. Not enough water pressure to fill tank F faster than Tank L. Correct me if I’m wrong.

  9. “Which Tank Fills Up First,” is wrong. But thank you for putting the wrong answer there. I can tell which students are cheating and looking stuff up on their phones instead of applying what I’ve tried to teach in class. Yes, I’m a Physics Teacher. And yes, the correct answer is “K.” But please don’t change it – gives me a teaching moment about cheating….just saying.

    • Tank I cannot fill up anything until J is almost full since water will not travel upwards, and for water to reach the top of linking pipe (i and j), then it has to rise at the same level as j. Therefore k is the wrong answer!!!

      • J only has to fill up a 1/3 before the weight shoots it up the left tube. K wins. Website, deduct a point please

  10. I would like to challenge the creator of the tanks filling up. I think the proper answer is k due to gravity mass. It would push it self threw I from j due to weight of water. Then it would slowly drip into k.

  11. You guys are a bunch of ……smart people…lol. The answer “is” F. The water will travel down from A into B then into C it can’t go into D because the path is blocked (notice the line blocking the fill point) from there it spills into J filling up about halfway then spilling into L where it maintains the level in J while filling the pipe connecting L to F (H is Blocked as is D) when full the water will begin filling F. F will fill and begin to over flow while L will fill to just below the fill pipe. J will never fill I. Water will always level itself if not forced and this is an example of gravity not force.

  12. If the inflow on the water puzzle is faster than the outflow, tank A would fill up first. One could assume, by the slow drip in the image, inflow was slow, but the puzzle did not specify.
    If one wanted to get real anal, it could be argued we do not know how long the water will run for… but that would be silly ;p

  13. Why do I think A will fill up first like if the amount of water flowing from the Tap is greater then the amount of the leak a will fill up first regardless of the leak…
    By the time water gets to F …. A will be filled long time…

  14. There’s a problem with the Matchstick 508 problem. By moving two matches from the 0, you can form 9E8 which equals 900,000,000. I’m not claiming that this is the highest number, but I am claiming it’s higher than the given solution. Perhaps they didn’t expect other number notations.

  15. seeing puzzle number 9 your answer and my answer

    your answer: The answer is the 44. Column1: [(7×4)+1]-11=18. Column2: [(8×5)+2]-12=30. Column3:

    my answer: The answer is 42.
    Row 1:2*(column number(2))=4 – value in first column(1)=3
    Row 2:5*(column number(2))=10 – value in first column(4)=6
    Row 3:8*(column number(2))=16 – value in first column(7)=9
    Row 4:12*(column number(2))=24 – value in first column(11)=13
    Row 5:30*(column number(2))=60 – value in first column(11)=42

    Formula works for all the previous results per row, so it should be valid also.

    • errata :
      seeing puzzle number 9 and your solution, I thought it differently and came up with another that I guess would be also correct maybe you should include it in the answer.

      your answer: The answer is the 44. Column1: [(7×4)+1]-11=18. Column2: [(8×5)+2]-12=30. Column3:

      my answer: The answer is 42.
      Row 1:2*(column number(2))=4 – value in first column(1)=3
      Row 2:5*(column number(2))=10 – value in first column(4)=6
      Row 3:8*(column number(2))=16 – value in first column(7)=9
      Row 4:12*(column number(2))=24 – value in first column(11)=13
      Row 5:30*(column number(2))=60 – value in first column(18)=42

      Formula works for all the previous results per row, so it should be valid also.

  16. In a real matchstick game situation, the sticks are laid on a table, or such, and people sit around. People in the opposite read the number as 805 instead of 508. from this angle, the answer will be 81151 (ordinary number) or 8E9 (scientific)

  17. The correct answers on most of these puzzles require making assumptions that are not provided by the problem. You could just as easily choose to make different assumptions and therefore get different answers.

    • You are totally correct, Noah! There is not one correct answer to a lot of these “puzzles.” Take the Logical Puzzle. Answer 1- could be 67 (Order of Operations – PEMDAS). Answer 2 – could be 38. Answer 3 could be 35. And the one I like best is Answer 4 – there is no answer because the pics are different in the final line and, therefore, have no value because we weren’t given any way to reference what the new pics should equal. Therefore, there is no way to answer this problem.

  18. Matchsticks 508 puzzle. You can take off 2 sticks from zero and put it before number 5 to make it 15118 then reverse the matchsticks making it 81151 as the highest possible answer.


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