Answer:
Explanation:
This method is known as dimensional analysis. Where a unit (and its number) appears in the numerator of a fraction, it appears in the denominator of the next fraction. You should always carry the units from 1 fraction to the next.
25 m 1 km 3600 seconds
==== * [ ====== ] * [==========]
sec 1000 m 1 hour
Notice how the units are going to cancel. What you are left with is
25 m * 3600 * 1 km
==============
sec 1000 m * 1 hour
90000 km
======
1000 hour
90 km / hour