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.
??
Puzzle 2
Can you find a five-digit number that has no zeros, no ones, no digit is repeated, and:
The fourth digit is a quarter of the total of all of the digits.The second digit is twice the first digit.The third digit is the largest.The last digit is the sum of the first two digits.
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.
??
Puzzle 3
What 5-digit number am I thinking of?
It has two prime digits.Digit 3 is the highest digit.Digit 2 is the lowest digit.Digit 1 is higher than the sum of digits 4 and 5.Digit 5 is half of digit 4.Digit 1 is one smaller than digit 3.Digit 5 is between digit 2 and digit 1
The digit 0 doesn't appear, and there are no duplicates. Don't forget that 1 isn't prime, the prime numbers start with 2, 3, 5, …
The total distance was 180 miles, but as I still had 5 miles to go, the required answer is 175 miles.
Reasoning
Let's try working backwards.
Day 4: I travelled 3/4, which means that the other 1/4 was 5 miles, and 20 miles were left at the start of day four.
Day 3: I travelled 2/3, which means that the other 1/3 was 20 mile, and 60 miles were left at the start of day three.
Day 2: I travelled 1/2, which means that the other 1/2 was 60 miles, and 120 miles were left at the start of day two.
Day 1: I travelled 1/3, which means that the other 2/3 was 120 miles, and 180 miles were ahead at the start of day one.
The full distance was therefore 180 miles, but we were asked how many miles I had travelled so far, and as I still had 5 to go the answer is 175 miles.
Double-Checking
Start distance: 180 miles.
Day 1: I travelled 1/3 of the distance (60 miles), leaving 120 miles.
Day 2: I travelled 1/2 of the distance (60 miles), leaving 60 miles.
Day 3: I travelled 2/3 of the distance (40 miles), leaving 20 miles.
Day 4: I travelled 3/4 of the distance (15 miles), leaving 5 miles.
