Random Puzzles 

Workings

Hint
Where on Earth is everything South?

Answer
The North Pole.

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
The first letters of one half of the words are: A, B, D, C, F, D, H, A, I.

Answer
ABUNDANT   + SCARCE
BRAVERY    + COWARDICE
DANGER     + SAFETY
CONTRACT   + EXPAND
FAMOUS     + UNKNOWN
DISTRIBUTE + GATHER
HORIZONTAL + VERTICAL
ACCIDENTAL + INTENTIONAL
IGNORANCE  + KNOWLEDGE

Workings

Hint
It doesn't matter how far it was to Manchester, so you can use any distance.

Answer
Billie.

Reasoning
If we call the one way distance T, we know that:

On the way there, Alex drove 90 miles, and Billie drove (T − 90) miles.

On the way back, Alex drove (T − 100) miles, and Billie drove 100 miles.

So, in total, both ways:

   Alex drove 90 + (T − 100)
      = T − 10

   Billie drove (T − 90) + 100
      = T + 10

Therefore, Billie drove 20 miles more than Alex.