How many miles are covered in a 20 kilometer race?

Approximately ##12.4##

##1## mile is exactly ##1.609344## kilometers.

So ##20## kilometers is ##20/1.609344 ~~ 12.4## miles.

##color(white)()##Bonus

Approximate mile ##harr## kilometer conversions can be made using the Fibonacci sequence:

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

Each term of the Fibonacci sequence is the sum of the previous two terms.

The ratio between pairs of successive terms tends to the "golden ratio" ##~~ 1.618##, which is quite close to ##1.609344##.

So we find that ##5## miles is about ##8## kilometers, ##21## kilometers is about ##13## miles, etc.

In the case of ##20## kilometers, we can approximate by:

##20 = 21 - 2/2 rarr 13 - 1/2 = 12.5##

or:

##20 = 21 - 5/5 rarr 13 - 3/5 = 12.4##