Random Puzzles 

Workings

Hint
Pages 1-9 are one digit each.

Answer
There are 65 pages and the number 9 appears six times.

Reasoning
The 65 pages are (with the six 9's highlighted):

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65.

If we remove the spaces, we get:

1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465. Which is 121 digits.

Workings

Hint
How many chocolates can they eat in one hour?

Answer
2 hours.

Reasoning
In one hour, Alex eats 27 chocolates, Billie eats 12, and Charlie eats 21.

A total of 60 chocolates.

Therefore, 120 chocolates would take 2 hours.

Workings

Hint
The code has just four letters, A, B, C, and D. Each letter encodes 5 different letters.

Answer
I think, therefore I am.

Reasoning
A represents a, b, c, d, and e.
B represents f, g, h, i, and j.
C represents k, l, m, n, and o.
D represents p, q, r, s, and t.
E represents u, v, w, x, and y.

Workings

Hint
A tricky base 8 question.

Answer
61.

Each term is a square expressed in base eight, 7 2=49 = 61 in base 8.