Kusum always forgets how to convert miles to kilometres and back again. However, she remembers that her car’s speedometer shows both miles and kilometres. She knows that travelling 50 miles per hour is same as travelling 80 kilometres per hour. To cover a distance of 200 km, how many miles Kusum would have to go?
50 miles per hour is same as travelling 80km per hour.
So, 1 km covers distance in 1h to 
miles.
To cover a distance of 200 km = 
Hence, 125 miles Kusum has to go for 200km.
105