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Chapter 3 Unit conversions
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Conversions It is frequently useful and sometimes necessary to convert from one set of units to another, e.g., hours to minutes, years to days, feet to meters, etc. Sometimes, conversions are intuitive; other times, less so.
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Example How many feet are in two miles? Set up a grid 2 miles Original
number Original units
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Example How many feet are in two miles?
2) Establish a conversion factor 2 miles 5280 Feet 1 Mile 5,280’ per mile Note: target unit is in the numerator Note: original unit is in the denominator
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Example How many feet are in two miles?
3) Multiply the numbers and units across the top row 4) Divide by the numbers and units in the bottom row. 2 miles 5280 Feet 2*5280 mile*feet 1 Mile mile
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Example How many feet are in two miles?
5) All but target units cancel. 2 miles 5280 Feet 2*5280 mile*feet 1 Mile mile
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Example How many hours in 50 seconds? Set up a grid 50 seconds
Original number Original units
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Example How many hours in 50 seconds? 2) Establish a conversion factor
1 min 1 hr 60 60 min 1 minute per 60 seconds; 1 hr per 60 seconds Note: target unit is in the numerator Note: original unit is in the denominator
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Example How many hours in 50 seconds?
3) Multiply the numbers and units across the top row 4) Divide by the numbers and units in the bottom row. 50 s 1 min 1 hr s*min*hr 60 60 min 3600 s*min
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Example How many hours in 50 seconds? 5) All but target units cancel.
1 min 1 hr s*min*hr 60 60 min 3600 s*min
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Example If you travel 50 mph, how far do you travel each second?
Set up a grid 50 miles 5280 feet 1 hr hour mile 3600 s Original number Original units
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Example If you travel 50 mph, how far do you travel each second?
2) Establish a conversion factor 50 miles 5280 feet 1 hr hour mile 3600 s 1 minute per 60 seconds; 1 hr per 60 seconds Note: target unit is in the numerator Note: original unit is in the denominator
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Example If you travel 50 mph, how far do you travel each second?
3) Multiply top row. 4) Divide by bottom row. 50 miles 5280 feet 1 hr 50*5280*1 miles*feet*hr hour mile 3600 s 1*3600 hr*mile*s
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Example If you travel 50 mph, how far do you travel each second?
5) All but target units cancel 50 miles 5280 feet 1 hr 50*5280*1 miles*feet*hr hour mile 3600 s 1*3600 hr*mile*s
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