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SI and Imperial Conversions . Ch. 3 Measurement. SI and Imperial Conversions. Sometimes we may need to convert from SI units to Imperial, or from Imperial to SI units. To do this, we will require a chart that describes the basic conversion factors:. Conversion Chart.
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SI and Imperial Conversions Ch. 3 Measurement
SI and Imperial Conversions • Sometimes we may need to convert from SI units to Imperial, or from Imperial to SI units. To do this, we will require a chart that describes the basic conversion factors:
Conversion Chart *note: These conversions are approximate. oz = ounce, lb = pound, gal = gallon
To convert between units, we will use proportions: • 1) Set up a fraction : Place an “x” and the units for what you WANT. • 2) Find the appropriate conversion on the chart. • 3) Set up a second fraction, with the units of what you WANT in the numerator and what you HAVE in the denominator • 4) Cross multiply and divide to get the correct answer.
Ex1. Carlos measures 14 cm but he needs to know this length in inches. How many inches is 14 cm? • 14cm = _______in ? • 1) WANT inches HAVE centimeters • 2) we are converting from SI imperial, so we will use: 1 cm = 0.394 in
Ex. 1 Continued • 3) • 4) • 14 x 0.394 1 = 5.52 in*note: rounded to 2 decimal places* • There are 5.52 in. in 14 cm. OR ~ 5 in.
Ex2. You are on vacation in Hawaii and are going on a mountain hike. You read in the guide book that the hike is 3.5 miles. How many km is this? • 1) WANT kmHAVE mi • 2) we are converting Imperial SIso we will use: 1 mi = 1.609 km • 3) • 4) =3.5 x 1.609 1 = 5.63 km*note: rounded to 2 decimal places* • There are 5.63 km in 3.5 miles.
But what if…? • We may need to complete more than one conversion if what we want is not on the conversion factor chart. • For example, you may need to change from Imperial SI first , then convert the SI units to the desired unit.
Ex3. Edmund is measuring wood planks to make a chair. He measures a piece to be 0.8 m, but he needs to know how many inches this will be. • 1) We WANT incheswe HAVE meters. • BUT there is no conversion on the chart from meters to inches. We must first convert m ft then ft in. • 2) SI Imperial so we will use: 1 m = 3.281 ft
Ex. 3 Continued • 3) • 4) = 0.8 x 3.281 1 = 2.62 ft • We must now convert from ftin • 2.62 ft x 12 = 31.44 in OR ~31in
We could have converted the SI units first (from m cm) and then converted from SIImperial. Let’s try it! • 1) 0.8 m = ____cm? K H D m d c m 0.8 x 100 = 80 cm • 2) SI Imperial, so we will use: 1 cm = 0.394 in
3) • 4) = 80 x 0.394 1 = 31.52 in. OR ~31in