Chapter 3
Unit Question
What are the uses of division in
Algebra?
Open Learning Logs
Date on Left…Section 3 – 8 on right
Warm-Up
Section 3 - 8
14
18
1) Are the fractions
and
equal?
49
56
Explain your answer.
2) Three apples cost $0.60. How much will a
dozen apples cost?
Section 8
What are proportions?
How do we use them to solve
problems?
Homework Clicky
Means – Extremes Property:
For all Real numbers, a, b, c, d with b, d ≠ 0
a c

If
then ad  bc
b d
Means-Extremes Property is just
Cross Multiplying
fancy schmancy words for_________________
Solve using Means-Extremes (Cross Multiplying)
2 4

3 a
4b 4

5 10
2a  12
2
2
40b  20
40 40
a6
1
b
2
5 x 8

2 4
5(4)  2( x  8)
 20  2 x  16
 16
 16
 4  2x
2
2
2 x
Solve using Means-Extremes (Cross Multiplying)
2
8

2c c 8
2(c  8)  8(2  c)
2c 16  16  8c
 8c
 8c
10c 16  16
 16  16
10c  32
10 10
c  3.2
d 4

9 d
d 2  36
Remember?
d 2   36
d  6
Darla drives 283.5 miles on 9 gallons of gas. If
CONDITIONS REMAIN THE SAME, how far could
Darla drive with 14 gallons of gas?
If we let the 1st sentence = 2nd sentence
and let x = miles to be driven on 14 gallons of gas
miles
miles

gallons gallons
283.5miles
x

9 gallons
14 gallons
9x  3969
9
9
x  441
Darla can drive 441
miles on 14 gallons
of gas.
Scale Drawings…
Drawing of a locomotive…
Scale:
.125 inch = 1 foot
If the drawing is
6.75 inches long,
what is the actual
size of the train?
SCALE = DRAWING
inches inches

feet
feet
0.125 6.75

1
x
0.125x  6.75
0.125 0.125
x  54
The train is 54 feet long
Homework
• Do HoffmaSheet 3 – 8
Homework
• Quiz Prep 3-5 to 3-8