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Dimensional Analysis. Using units to solve problems 2.5 m X 1km = 0.0025 km 1000 m Conversion Factor – Used to change from one unit to another. Top equals the bottom Conversion factors = 1. Example. How many seconds are in 3 hours? s min hr
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Dimensional Analysis Using units to solve problems 2.5 m X 1km = 0.0025 km 1000 m Conversion Factor – Used to change from one unit to another. Top equals the bottom Conversion factors = 1
Example How many seconds are in 3 hours? s min hr (X) (3) 3hr X 60 min X 60 s = 10,800 s 1 hr 1 min
Procedure • Write down each unit in the problem once. • Draw lines to show conversion factors. • Use units to set up problems. • Put in numbers and solve.
Practice Convert 10 cm to km cm m km
Convert 10 cm to km 10 cm X 1 m X 1km = 100 cm 1000 m 10 cm = 0.0001 km
How many minutes are in 2.5 hours? Conversion factor 2.5 hr x 60 min = 150 min 1 hr cancel By using dimensional analysis / factor-label method, the UNITS ensure that you have the conversion right side up, and the UNITS are calculated as well as the numbers!
Sample Problem • You have $7.25 in your pocket in quarters. How many quarters do you have? 7.25 dollars 4 quarters 1 dollar = 29 quarters X
You Try This One! If Jacob stands on Spencer’s shoulders, they are two and a half yards high. How many feet is that?
Learning Check A rattlesnake is 2.44 m long. How long is the snake in cm? a) 2440 cm b) 244 cm c) 24.4 cm
Solution A rattlesnake is 2.44 m long. How long is the snake in cm? b) 244 cm 2.44 m x 100 cm = 244 cm 1 m
Learning Check How many seconds are in 1.4 days? Unit plan: days hr min seconds 1.4 days x 24 hr x ?? 1 day
How many gits equal 5 hews? • 20 gits equal 1 erb • 1 futz equals 2 hews • 10 erbs equal 1 futz
How many drams is 4.0 grams? • 1 pound = 7000 grains • 16 ounces = 1 pound • 3 scruples = 1 dram • 454 grams = 1 pound • 30 grams = 1 scruple
A blacksmith has to put new shoes on a stable of 20 horses. Each shoe requires 3 nails. How can he or she calculate the number of nails that must be brought to the stable?