IQ Test DK, answers and reasoning.
The knowledge in this post is presented based on the following link. I'll explain the logic behind its final and hardest puzzles.
30 A - Pay careful attention to the images. Images in the middle are shrunk when they combine with the image on the left to form the image on the right. The middle image is reduced to the size of the image on the left, resulting in a square of the same size and an additional black ball.
31 D - Images in each corner are formed by two combined shapes from their nearest respective directions.
32 E - Obvious, one segment moves each time.
33 G - There are three separate patterns, each is placed at a certain angle.
34 G - The middle circle acts as a + or - function. Balls outside are minus, inside are addition.
35 C - There's a pivot in each arrow, for the two patterns above it's in the middle, for the third it's in the bottom right.
36 F - Imagine it's a bar chart. In patterns, the largest 'bar' appears three times, and one and two sized bars appear twice. Using these patterns you can deduce that the answer must be F.
37 H - The entire image is a continuous pattern. A black square appears every turn. There are two balls that move one space right every turn. When they pass a black square, they are not only invisible, but they change colous when they emerge.
38 F - The arrow not only enlargens but changes orientation too.
39 B - Each symbol moves right one space per turn. Triangles turn to Xs, Xs to Os, and Os to triangles.