A man spends one fifth of the money in his wallet.
He then spends one fifth of what remains in the wallet.
He spends $36.00 in all.
How much money did he have to begin with?

All students in the physics class also study mathematics. Half of those who study literature also study mathematics. Half of the students in the mathematics class study physics. Thirty students study literature and twenty study physics. Nobody who studies literature studies physics. How many students in the mathematics class study neither physics nor literature?

Mathematical aptitude tests frequently have sets of numbers where you are supposed to figure out a pattern or guess the next number. For example,

• (2, 4, 6, 8, 10)  is a list of even numbers corresponding to 2×n  for n=1, 2, 3, …

• (1, 1, 2, 3, 5)  is the well-known Fibonacci series where two adjacent numbers are added to produce the next number.

• (2, 3, 5, 7, 11)  is a list of prime numbers.

• (1, 2, 4, 8, 16)  is an exponential series corresponding to 2ⁿ  for n=0, 1, 2, …

Can you figure out the special significance of the following sequence?
(2, 6, 10, 15, 19