SI and Imperial Conversions
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Transcript SI and Imperial Conversions
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
Conversion Factors
Length
Imperial SI
Capacity/ Volume
SI Imperial
Imperial SI
1 gal = 4.546 L
SI Imperial
1 in = 2.54 cm
1 cm = 0.394 in
1 L = 0.22 gal
1 ft = 0.305 m
1 m = 3.281 ft
1 yd = 0.914 m
1 m = 1.094 yd
Imperial SI
SI Imperial
1 mi = 1.609 km
1 km = 0.621 mi
1 oz = 28.35 g
1 g = 0.0305 oz
1 lb = 0.454 kg
1 kg = 2.205 lb
1 lb = 454 g
1 g = 0.002 lb
Mass/Weight
*note: These conversions are approximate. oz = ounce, lb = pound, gal = gallon
To convert between units, we will use
proportions:
W ANT
1) Set up a fraction : H A V E 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
x _ in
14 cm
2) we are converting from SI imperial, so
we will use: 1 cm = 0.394 in
Ex. 1 Continued
3)
0 .3 9 4 in
4)
x _ in
1cm
14 cm
0.394 in
1cm
14 x 0.394 1 = 5.52 in
*note: rounded to 2 decimal places*
There are 5.52 in. in 14 cm. OR ~ 5
1
2
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 km HAVE mi
x _ km
3.5 m i
2) we are converting Imperial SI so we
will use: 1 mi = 1.609 km
1.609 km
3)
1m i
1.609 km
x _ km
4)
3.5 m i
=
1m i
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 inches we 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
x _ feet
0 .8 m
Ex. 3 Continued
3.281 feet
3)
4) x _
1m
feet
0 .8 m
=
3.281 feet
0.8 x 3.281 1 = 2.62 ft
1m
We must now convert from ftin
7
2.62 ft x 12 = 31.44 in OR ~3116 in
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?
0.8 x 100 = 80 cm
KHDmdcm
x _ in
80 cm
2) SI Imperial, so we will use:
1 cm = 0.394 in
3)
0 .3 9 4 in
1cm
x _ in
4)
80 cm
=
0 .3 9 4 in
1cm
31.52 in. OR ~31
80 x 0.394 1 =
1
2
in