Mathematical Puzzles 

Workings

Hint
How many games took place?

Answer
3.

Reasoning
There were 5 teams in the league, and every team played every other, so there were a total of 10 games played:
   Rugby     vs  Grimsby
   Rugby     vs  Hereford
   Rugby     vs  Lichfield
   Rugby     vs  Reading
   Grimsby   vs  Hereford
   Grimsby   vs  Lichfield
   Grimsby   vs  Reading
   Hereford  vs  Lichfield
   Hereford  vs  Reading
   Lichfield vs  Reading

We know that 2 points were allocated for each game played. Which means that there were a total of 20 points over the 10 games.

Since the given results add to 17, the remaining 3 points belong to Reading.

Workings

Hint
Try working backwards.

Answer
120 miles.

Reasoning
I now have 5 miles left to travel, so I must have travelled 5 miles yesterday.

At the end of Day 3, I had 10 miles left to travel, so I must have had 40 miles left at the start of the Day 3.

At the end of Day 2, I had 40 miles left to travel, so I must have had 60 miles left at the start of the Day 2.

At the end of Day 1, I had 60 miles left to travel, so I must have had 120 miles left at the start of the Day 1.

Double-Checking
On the Day 1, I travelled 60 miles, leaving 60 miles.

On Day 2, I travelled 20 miles, leaving 40 miles.

On Day 3, I travelled 30 miles, leaving 10 miles.

Yesterday, I travelled 5 miles, leaving 5 miles.

Workings

Hint
Start by labelling the number as ABCDE.

Answer
24976.

Reasoning
We can start by labelling the digits as ABCDE.

We know that:

(i)  B = 2 x A

and:

     E = A + B

And using (i) we get:

     E = A + (2 x A)
(ii) E = 3 x A

If A = 1, this isn't allowed (as there are no 1's in the puzzle).

If A = 2, then B = 4, and E = 6.

If A = 3, then B = 6, and E = 9, but this isn't allowed (as C has to be the largest digit).

So, A = 2, B = 4, E = 6, and we now have to find C and D.

We also know that:

D = (A + B + C + D + E) ÷ 4

And using (i) and (ii) we get:

D = [A + (2 x A) + C + D + (3 x A)] ÷ 4

so:

3 x D = (6 x A) + C

so:

(iii) D = [(6 x A) + C] ÷ 3

C can only be 7, 8 or 9 (as it's the largest digit, and we've already found 6) and (iii) tells us that it must be a multiple of 3, which means that C = 9. Leaving D = 7.

So the final number is: 24976.

Double-Checking
The answer is 24976.

The fourth digit is a quarter of the total of all of the digits.
   A + B + C + D + E = 2 + 4 + 9 + 7 + 6 = 28, and 28 ÷ 4 = 7.

The second digit is twice the first digit.
   4 = 2 x 2.

The third digit is the largest.
   9 is the largest digit.

The last digit is the sum of the first two digits.
   6 = 2 + 4.

Workings

Hint
What can digits 4 and 5 be?

Answer
71842.

Reasoning
The number can be represented as:

   - - - - -

By (5), Digit 5 is half of Digit 4, so we have four possibilities:

   - - - 2 1
   - - - 4 2
   - - - 6 3
   - - - 8 4

By (4), Digit 1 is higher than the sum of Digit 4 and Digit 5, so we can eliminate two possibilities, leaving:

   - - - 2 1
   - - - 4 2

By (7), Digit 5 is between Digit 2 and Digit 1, so we can eliminate - - - 2 1, leaving:

   - - - 4 2

By (4), Digit 1 must be higher than the sum of Digit 4 and Digit 5, so we have three possibilities:

   7 - - 4 2
   8 - - 4 2
   9 - - 4 2

By (6), Digit 1 is 1 smaller than Digit 3 we can eliminate 9 - - 4 2, and fill in Digit 3, leaving:

   7 - 8 4 2
   8 - 9 4 2

By (3), Digit 2 is the lowest digit, and must be 1:

   7 1 8 4 2
   8 1 9 4 2

By (1), the only possibility is:

   7 1 8 4 2