Question

A car is traveling at 118 km/h. What is its speed in Mm/h

Answer 1

118x1000x100x10. This is so because 1km equals 1000m, 1m equals 100 cm, 1 cm equals 10mm. SO multiply to get answer.

Answer 2

I think 'Mm' means megameter. 1 megameter = a million meters, 1 * 10^6 m
A kilometer is 1000 meters = 1 * 10^3 meters

The 'mega' prefix comes after the 'kilo' prefix in standard prefix stuffs. Idk what it's called.
There are 1000 kilometers in a megameter, essentially.