Random Puzzles 

Workings

Hint
Look for the question.

Answer
N.

Reasoning
Starting with the first letter and taking every other letter gives: TO BE OR NOT TO BE TH

Starting with the second letter and taking every other letter gives: AT IS THE QUESTIO

Combining gives: TO BE OR NOT TO BE THAT IS THE QUESTIO, and the last letter of QUESTION is missing.

Workings

Hint
How many students study chemistry and physics, but not biology?

Answer
500 students.

Reasoning
The answer is more easily seen if three intersecting circles are drawn, and the numbers inside each section are worked out.

We know that 73 students study all three disciplines, which allows us to work out the numbers.

97 students study chemistry and physics, so 97 − 73 = 24 study just chemistry and physics.
138 students study physics and biology, so 138 − 73 = 65 study just physics and biology.
152 students study chemistry and biology, so 152 − 73 = 79 study just chemistry and biology.

280 students study chemistry, so 280 − 73 − 24 − 79 = 104 study just chemistry.
254 students study physics, so 254 − 73 − 24 − 65 = 92 study just physics.
280 students study biology, 280 − 73 − 65 − 79 = 63 study just biology.

For a total of: 104 + 92 + 63 + 24 + 65 + 79 + 73 = 500 students.

Workings

Hint
Try to rotate them around in your head, but watch out for mirror images.

Answer
A and C.

Workings

Hint
Sometimes the easiest explanations are the best.

Answer
The other end of the rope is not tied to anything!