Question

Approximately how many kilometers are covered in a 9 mile race?

Answer 1

Approximately `14.5`

Explanation:

`1` mile is exactly `1.609344` kilometers.

So `9` miles is exactly `9xx1.609344 = 14.484096` kilometers.

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Bonus

One way of approximating mile `harr` kilometer conversions is to use the Fibonacci sequence:

`1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144`

Each term in the Fibonacci sequence is the sum of the two previous terms. The ratio between pairs of terms tends towards the "golden ratio" `~~ 1.618`. Since this is close to `1.609`, we find that `5` miles is about `8` kilometers, `13` miles is about `21` kilometers, etc.

This is not so easy in the case of `9` miles, but we could do:

`9 = 8 + 2/2 rarr 13 + 3/2 = 14.5`

Or perhaps:

`9 ~~ 89/10 rarr 144/10 = 14.4`