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.
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Puzzle 726
Below you will find 10 well-known seven-letter words, with only their endings remaining.
Can you find the words? ----rem----oct----pso----dma----edo----rre----sfy----ott----hma----dpa
Reasoning
Q1 can't have A as its answer (otherwise it would contradict itself).
If Q1's answer was C (meaning Q4's answer was A), then Q3's answer would be C. However, Q2's answer should now be A, but this isn't allowed by Q1 (as Q4 is the first answer with A). This is a contradiction.
Therefore, Q1's answer is B (meaning Q3's answer is A).
For Q2's answer to be C, Q4's answer would have to be A, which would contradict Q4. Therefore, Q2's answer is B making Q4's answer B.
