Random Puzzles 

Workings

Hint

Answer
Tug-of-war.

Workings

Hint
Look at a keyboard?

Answer
8 F 7.

This is the sequence F7, F8, F9, F10, F11, F12, written backwards.

Often seen on a computer keyboard.

21F 11F 01F 9F 8F 7F

Workings

Hint
A little bit of algebra might help.

Answers
Drew is 7 years old. Glen is 4 years old.
Answer #1
The first question involves Drew (D) and Alex (A).

Drew is currently one fifth of Alex's age, so:

(1)      A = D x 5

In 21 years, Alex will be twice their age, so:

(2) A + 21 = (D + 21) x 2

Using (1) in (2) gives:

  A + 21 = (D + 21) x 2

 5D + 21 = (D + 21) x 2

 5D + 21 = 2D + 42

      3D = 21

       D = 7

So Drew is 7 (and Alex is 35).

Answer #2
The second question involves Glen (G) and Billie (B).

Billie is exactly seven times the age of Glen:

(3)     B = G x 7

In 8 years, Billie will be three times the age of Glen, so:

(4) B + 8 = (G + 8) x 3

Using (3) in (4) gives:

  B + 8 = (G + 8) x 3

 7G + 8 = (G + 8) x 3

 7G + 8 = 3G + 24

     4G = 16

      G = 4

So Glen is 4 (and Billie is 28).

Workings

Hint
2, 3, 5, 7, 11, 13, 17, 19, 23, …

Answer
29.

The first ten prime numbers are: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29.