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Chapter 2 Approaches to Problem Solving

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66/98 You are buying artificial turf to cover a game field that is 150 feet long ... 75/98 Suppose you drive a car with an average gas mileage of 28 miles per gallon. ... – PowerPoint PPT presentation

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Title: Chapter 2 Approaches to Problem Solving


1
Chapter 2Approaches to Problem Solving
  • Section 2A
  • The Problem Solving Power of Units
  • Pages 84-95

2
Units
  • The units of a quantity describe what is being
    measured or counted.
  • We can add or subtract numbers ONLY when they
    have the same units.
  • We can always multiple or divide numbers well
    just create new units.

3
For example
  • Travel 195 miles (distance)
  • Trip took 3 hours (time)
  • Average speed (distance/time)
  • 195 miles/3 hours
  • 65 mph (miles per hour)

4
For example
  • One side of the floor is 25 feet long
  • The other side is 30 feet long.
  • The area of the floor space
  • 25 ft 30 ft 750 ft2 (square feet)
  • The rooms height is 12 feet.
  • The volume of the room is
  • 25ft 30ft 12ft 9000 ft3 9000 cubic feet

5
2-A
6
Practice what units?
  • 19/96 The price of apples, found by dividing
    their
  • total cost in dollars by their total weight in
    pounds.
  • dollars per pound /lb
  • 1b/85 The area of a circle, found with the
    formula
  • where r is the radius of the circle measured in
    centimeters.
  • - square centimeters cm2
  • 27/97 The density of a rock, found by dividing
    its weight in grams by its volume in cubic
    centimeters.
  • grams per cubic centimeters g/c3 g/cc
  • pg85 The energy used by a light bulb found by
    multiplying the power rating in kilowatts by the
    number of hours it is turned on.
  • - kilowatt X hours kilowatt-hours

7
Unit Conversionsconverting one set of units to
another
2-A
  • Trick multiply by 1.

12 inches 1 foot
1 week 7 days
8
Unit Conversions
2-A
  • 30/97 Convert a distance of 18 yards into inches.

33/97 Convert a lot size of 1/5 acre to square
feet.(1 acre 43560 square feet)
38/97 A car is driving at 100 kilometers per
hour. What is its speed in kilometers per second?
44/97 A football field is 100 yards long and
60 yards wide. Find its area in square yards
and square feet. (Careful with square and cubic
units!)
9
Currency Conversions (www.xe.com on 8/29/06)
2-A
Currency dollars per foreign foreign per Dollar
British pound 1.89198 0.528548
Canadian dollar 0.899786 1.11138
European euro 1.27605 0.783671
Japanese yen 0.00855457 116.897
Mexican peso 0.0917226 10.9024

10
Currency Conversions
2-A
  • 49/97 Which is worth more today 1 British pound
    or 1 dollar? Explain.

51/97 You return from a trip with 2500 Mexican
pesos. How much are your pesos worth in ?
54/97 How many Canadian dollars can you buy for
100?
11
Problem Solving with Units
2-A
56/97 Apples in Japan sell for about 75 yen each.
If you buy 4 apples, how much have you spent in
dollars?
  • 57/98 A car travels 14 miles in 15 minutes. How
    fast is it going in miles per hour?
  • 59/98 You purchased 40 acres of farm land for
    200,000. How much did you pay per acre?
  • 61/98 You are buying 4.7 pounds of apples priced
    at 1.29 per pound. How much do you pay?
  • 66/98 You are buying artificial turf to cover a
    game field that is 150 feet long and 100 feet
    wide. The turf costs 7.50 per square yard. How
    much do you pay?

12
2-A
Problem Solving with Units
70/98 A human heart beats about 60 times per
minute. If an average human being lives to the
age of 75, how many times does the average heart
beat in a lifetime?
75/98 Suppose you drive a car with an average
gas mileage of 28 miles per gallon. If you plan
to take a 2500-mile cross country trip, how many
gallons of gasoline should you expect to use.
13
Homework
  • Pages 97-99
  • Part I 34, 45, 48, 53, 54 55, 58, 62, 65,
    68, 76
  • use the exchange rates given to you in class.
  • Part II 58, 60, 62, 65, 68, 76
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