First write down the desired quantity Unit Conversions Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) # km First write down the desired quantity
Next, equate desired quantity to the given quantity Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) # km = 47 mi Next, equate desired quantity to the given quantity
Now we have to choose a conversion factor Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) # km = 47 mi Now we have to choose a conversion factor
What conversion factors are possible? Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) # km = 47 mi 1 km 0.621 mi 0.621 mi 1 km What conversion factors are possible?
Pick the one that will allow you to cancel out miles Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) # km = 47 mi 1 km 0.621 mi 0.621 mi 1 km Pick the one that will allow you to cancel out miles
Pick the one that will allow you to cancel out miles Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) # km = 47 mi 1 km 0.621 mi 0.621 mi 1 km Pick the one that will allow you to cancel out miles
Cross out common factors Factor label example Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) x 1 km 0.621 mi # km = 47 mi Cross out common factors
Factor label example Now finish the math. Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) x 1 km 0.621 = 75.7 km # km = 47 Now finish the math.
Factor label example The final answer is 75.7 km Q - How many kilometers are in 47 miles? (note: 1 km = 0.621 miles) x 1 km 0.621 = 75.7 km # km = 47 The final answer is 75.7 km
Summary The previous problem was not that hard In other words, you probably could have done it faster using a different method However, for harder problems the factor label method is easiest
More examples You want to buy 100 U.S. dollars. If the exchange rate is 1 Can$ = 0.65 US$, how much will it cost? # Can$ = 100 US$ x 1 Can$ 0.65 US$ = 153.85 Can$
There are 12 inches in a foot, 0 There are 12 inches in a foot, 0.394 inches in a centimeter, and 3 feet in a yard. How many cm are in one yard? # cm = 1 yd x 3 ft 1 yd x 12 in 1 ft x 1 cm 0.394 in = 91.37 cm