Question

1 marathon is 26.2 miles. How long is half-marathon in kilometers

Answer 1

-21.097494 kilometers

Answer 2

If 1 marathon = 26.2 mi
1 half-marathon = 13.1 mi
1 km = 0.621 mi

Then 13.1 * 0.621 = the length of a half-marathon in kilometers, which is 21.082 km.