Using units to solve problems 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) 2440 cm b) 244 cm c) 24.4 cm 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
How many seconds are in 1.4 days? Unit plan: days hr min seconds 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 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?