Lets set up an equation to easier understand this.
1/1.5 = 3.7/x (x represents the unknown km)
We know that whatever you do to the top you do to the bottom.
And we can see that 1 x 1.5 = 1.5
So we can multiply the same thing by 3.7
1.5 x 3.7 = 5.55
So in this case you would travel 5.55 km in 3.7 seconds.
GOOD LUCK :)