Riddles with transformations

Puzzles, riddles, brain teasers, conundrums, logic questions in pictures. There are questions here with various types of transformations of geometric images. In these logic tasks, puzzles and brain teasers, transformation is indicated by an arrow from left to right. 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 - 20
In this challenging logic riddle-conundrum, there are small squares in the large square boxes on the left. The maximum number of small squares in one field can be 4*4 = 16. Try to understand the relationship between the images to the left and right of the arrows. Choose the correct answer for the bottom line.
Correct answer = 4.
The square cells on the left contain the initial set of squares. During the transformation, some changes occur: existing squares disappear, and missing squares appear. After this, the entire image is rotated clockwise by 90 degrees. This image is to the right of the arrow. The stages of transformation are shown below.
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