Tuesday, March 22, 2016
Unit Multipliers/Dimensional Analysis
(Saxon)
(Glencoe)
Converting units by using using
unit multipliers (which is
dimensional analysis)
Compute mentally:
What are units?
Units-- the words we attach to numbers.
Examples: 3 feet
10 inches
5 meters
Denominate number -- the number
Units -- the word
What are units?
Write the units on your white board.
4 yards
8 miles per hour
5,280 feet
U.S. Customary System
The basic units of measure we use for length are
related in the following ways:
12 inches = 1 foot
3 feet = 1 yard
5,280 feet = 1 mile
You should memorize these!
U.S. Customary System
The basic units of measure we use for weight are
related in the following ways:
16 ounces = 1 pound
2,000 pounds = 1 ton
You should memorize these!
What happens if you multiply
something by a fraction that equals 1?
What would number would
make each fraction equal to 1?
Unit Multipliers
Unit Multipliers can be written two ways.
Using Unit Multipliers
Unit multiplier
•
Unit multiplier
•
5 ft
12 in
= 60 inches
• 1 ft
1
Notice that the units “ft” cancel.
Yes, you can think this through without a unit
multiplier. “I know there are 12 inches in every
foot, so if I have 5 feet I will have 5 times 12
inches.
However, for this assignment, USE unit multipliers.
And…SHOW YOUR WORK!!!!!!!!!!!!
Another example:
•
•
•
What if?
What if we had used the unit multiplier
with yards on the bottom?
420 ft
1
•
3 ft
= 1260 ft • ft
1 yd
1 yd
Your Turn on the White Board
Use a unit multiplier to convert 72 inches
to feet.
Answer: 6 ft
Your Turn on the White Board
Use a unit multiplier to convert 4.6 miles to feet.
Answer: 24,288 ft
Your Turn on the White Board
Use a unit multiplier to convert 4 tons to pounds.
Answer: 8000 lb
Classwork Time
• Show your work with unit multipliers
even if you can convert these in your
head.
What you have
(number and units)
1
x
Units you desire
Units you have