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Workings

Hint
Try working backwards.

Answer
7,340 metres.

Reasoning
Stage 5's clue tells us that 150m was left. So the distance left at the start of Stage 4 must have been:
Dist4 = Dist4 + 75 + 150
        —————
          2

Which simplifies to give Dist4 = 450m.

Stage 3's clue tells us that 450m was one quarter of the remaining distance, so Dist3 = 1,800m.

Stage 2's clue tells us that the distance at the start of Stage 2 was:
Dist2 = Dist2 + 35 + 1800
        —————
          2

Which simplifies to give Dist2 = 3,670m.

Stage 1's clue tells us that 3,670m was half the overall distance, which means the entire ride was 7,340m.

Double-Checking
Starting with 7,340m:
Stage 1: cycled 3,670m, leaving 3,670m

Stage 2: cycled 1,870m, leaving 1,800m

Stage 3: cycled 1,350m, leaving   450m

Stage 4: cycled   300m, leaving   150m

Stage 5: cycled   150m, leaving     0m

Workings

Hint
Can you see 1, 2, 3, …?

Answer
46.

Reasoning
Take the numbers in pairs, square the first, and reverse the digits.
1  1   (1 x 1 = 1,  reversed is 1)
2  4   (2 x 2 = 4,  reversed is 4)
3  9   (3 x 3 = 9,  reversed is 9)
4  61  (4 x 4 = 16, reversed is 61)
5  52  (5 x 5 = 25, reversed is 52)
6  63  (6 x 6 = 36, reversed is 63)
7  94  (7 x 7 = 49, reversed is 94)
   so we require:
8  46  (8 x 8 = 64, reversed is 46)

Workings

Hint
What must the middle temperature be? Remember that the temperature are in degrees Celsius.

Answer
The temperatures were -6, -2, 2, 6, 10 °C.

Each day increased by a steady 4 degrees.

Reasoning
As the temperature rose steadily each day, we know that the middle temperature (Day 3) was 2 degrees (because the average was 2 degrees).

Since Day 3 was 2 degrees, and there were two negative temperatures, we know that the daily increase must have been at least 3 degrees (otherwise Day 2 would not have been negative).

If we check a daily increase of 3 degrees, the sequence would be -4, -1, 2, 5, 8, but this doesn't work as the product is less than 500.

If we check a daily increase of 4 degrees, the sequence would be -6, -2, 2, 6, 10, which does matches all of the requirements.

If we check a daily increase of 5 degrees, the sequence would be -8, -3, 2, 7, 12, but this doesn't work as the product is more than 2000.

Any larger increase makes the product even larger, so we can stop checking.

So the only possible answer is -6, -2, 2, 6, 10.

Workings

Hints
The first letters of the words are: P, O, B, C, U, R, D, V, D, D, N, S, B, T, D.

Answers
---cil = pencil ---hid = orchid ---nze = bronze ---ese = cheese ---lug = unplug ---som = ransom ---uxe = deluxe ---uum = vacuum ---arm = disarm ---amo = dynamo ---rby = nearby ---ink = shrink ---sai = bonsai ---too = tattoo ---fen = deafen