Random Puzzles 

Workings

Hint
Both words begin with the letter B.

Answer
Brainy and binary.

Workings

Hint
A little bit of algebra might help.

Answer
There are four boys and three girls.

If we call the number of boys B, and girls G.

From the first statement (we take one off as Billy is a boy):

              B - 1 = G

and similarly:

        2 x (G - 1) = B

Substitute G from the first equation into the second equation to give:

  2 x ((B - 1) - 1) = B

    2 x (B - 1) - 2 = B

      2 x B - 2 - 2 = B

          2 x B - 4 = B

                  B = 4

which means that B = 4 and hence G = 3.

Workings

Hint
A very common sequence, but in base 8!

Answer
13.

Odd numbers expressed in base 8, 11 in base 8 = 13.

Workings

Hint
Think of the pages from 1-9, and then 10-99.

Answers
There are 147 pages. The number 3 appears 35 times.
Answer #1
For pages 1-9, there are 9 pages, which is 9 digits.

For pages 10-99, there are 90 pages, which is 180 digits.

This is a total so far of 189, therefore we require another 333 – 189 = 144 digits, which is another 144 ÷ 3 = 48 pages.

Taking us to 9 + 90 + 48 = 147 pages in total.

Answer #2
From page 1 to 147 we have 15 pages that end in 3:

   3, 13, 23, …, 143

We also have the ten pages that start with 30:

   30, 31, 32, …, 39

Plus the ten pages that start with 130:

   130, 131, 132, …, 139

For a total of 15 + 10 + 10 = 35 number 3's.