Multiply by 1 in disguise — that's all unit conversion is.
A conversion factor is a fraction equal to 1, where the numerator and denominator are the same quantity in different units. Multiplying by a conversion factor changes the unit without changing the actual measurement. You can chain multiple conversion factors together.
Dimensional Analysis Method
60 miles/hour × (5,280 feet/1 mile) × (1 hour/60 minutes) = (60 × 5,280 × 1) / (1 × 1 × 60) feet/minute = 316,800 / 60 = 5,280 feet per minute
Remember This!
Cross out units that appear in both numerator and denominator as you go. If the remaining unit is not what you want, flip the conversion factor.
How many seconds are in 2.5 hours? (1 hour = 60 minutes, 1 minute = 60 seconds)