Difficult puzzles, brain teasers and conundrums

Puzzles, riddles, brain teasers, conundrums, logic questions in pictures. All the logic questions here are more difficult than the average in other sections of the site. You will most likely need more time to complete them than usual. But you can look at the answers and explanations for all these logic riddles, brain teasers and conundrums. To check your answer, click on the «Answer» button located below the task. After this, the correct answer and explanations will appear. Below you can select other questions on this topic. Typically each topic has 20 questions or more. At the same time, the complexity of logical problems gradually increases. First there will be easy questions, then medium, then difficult. Try to complete tasks as quickly as possible.
Question - 6
This logic riddle has five equations containing different images that are made up of lines. Each image corresponds to a number. You must understand the rule that these images correspond to numbers. Next, you need to indicate a suitable number that can replace the question mark. There are six answer options in total.
Correct answer = 16. Option number 1.
Here, in each geometric figure, the number of angles with a value of 90 degrees is counted. The number of such angles in each image is shown below.
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