1. 4.7 Ratios, Proportions, & Converting Units of Measure
Today’s Date:
12/1/17

2. Ratios
Ratio of a to b
quotient
If 2 measurements are same type, need same units
Ratio of 1 yard to 18 inches (both measure length)
3 ft = 1 yd & 12 in = 1 ft → 3(12) inches in 1 yd

3. Ex 1) Express 60 miles per hour in terms of feet per second
5280 feet = 1 mile
60 sec = 1 min
60 min = 1 hour
Need to cancel miles & hour
→ Multiply by “fancy” 1
Since hour is in denom, write ratio with hours in numerator so they cancel
We are left with feet in numerator & seconds in denominator, which is what we want

4. Proportions
Proportion: equality of 2 ratios
a is to b as c is to d

5. Example 2
If a car moves at a uniform rate of speed & travels 400 km in 8 hours, how far does it travel in 6 hours?
Word Ratio:
Cross Multiply

6. Measurement Conversions
12 inches = 1 foot
3 feet = 1 yard
5280 feet = 1 mile
100 cm = 1 meter
1000 m = 1 km
16 ounces = 1 pound
2000 lbs = 1 ton
4 quarts = 1 gallon
2 pints = 1 quart
16 ounces = 1 pint
60 sec = 1 min
60 min = 1 hour

7. Homework
#408 Pg – 18 all