4-4 Solving Proportions Warm Up Warm Up Lesson Presentation Lesson Presentation Problem of the Day Problem of the Day Lesson Quizzes Lesson Quizzes
Dec 22, 2015
4-4 Solving Proportions
Warm UpWarm Up
Lesson PresentationLesson Presentation
Problem of the DayProblem of the Day
Lesson QuizzesLesson Quizzes
4-4 Solving Proportions
Warm UpDetermine whether the ratios are proportional.
1. 58
, 1524
2. 1215
, 1625
3. 1510
, 2016
4. 1418
, 4254
yes
no
yes
no
4-4 Solving Proportions
Problem of the Day
If A = 1, B = 2, C = 3, D = 4, and so on, all the way to Z = 26, then what is A + B + C + D + . . . + Z = ? (Hint: A + Z = B + Y.)
351
4-4 Solving Proportions
MA.7.A.1.1 …Use proportions to solve problems.Also MA.7.A.1.6
Sunshine State Standards
4-4 Solving Proportions
Vocabularycross product: the product of the numerator in one ratio
and the denominator in the other
4-4 Solving Proportions
For two ratios, the product of the first term in one ratio and the second term in the other is a cross product. If the cross products of the ratios are equal, then the ratios form a proportion.
5 · 6 = 30
2 · 15 = 30=2
56
15
4-4 Solving Proportions
You can use cross products to solve proportions with variables.
4-4 Solving Proportions
Use cross products to solve the proportion.
Additional Example 1: Solving Proportions Using Cross Products
15 · m = 9 · 5
15m = 45
15m15
= 4515
m = 3
The cross products are equal.
Multiply.
Divide each side by 15 to isolate the variable.
= m5
915
4-4 Solving Proportions
Check It Out: Example 1
Use cross products to solve the proportion.
6·14 = 7m;m = 12=
67
= m14
847
A.
B.
9·7 = 6r;r = 10.5=
96
= r7
636
4-4 Solving Proportions
It is important to set up proportions correctly. Each ratio must compare corresponding quantities in the same order.
Suppose a boat travels 16 miles in 4 hours and 8 miles in x hours at the same speed. Either of these proportions could represent this situation.
16 mi4 hr
= 8 mix hr
16 mi8 mi
= 4 hrx hr
4-4 Solving Proportions
Additional Example 2: Problem Solving Application
If 3 binders of the same size take up 4 inches of space on a shelf, how much space will be needed for all 26 of these binders?
11 Understand the Problem
Rewrite the question as a statement.• Find the space needed for 26 binders.
List the important information:• 3 binders take up 4 inches of space.
4-4 Solving Proportions
22 Make a Plan
Set up a proportion using the given information. Let x represent the inches of space needed.
3 binders4 inches
= 26 bindersx
bindersinches
Additional Example 2 Continued
4-4 Solving Proportions
Solve33
34
= 26x
3 · x = 4 · 26
3x = 104
3x3
= 1043
x = 34 23
She needs 34 23
inches for all 26 binders.
Write the proportion.
The cross products are equal.
Multiply.
Divide each side by 3 to isolate the variable.
Additional Example 2 Continued
4-4 Solving Proportions
Look Back44
34
= 2634 2
3
4 · 26 = 104
3 · 34 23
= 104
The cross products are equal, so 34 23
is theanswer
Additional Example 2 Continued
4-4 Solving Proportions
Check It Out: Example 2A
A stack of 33 CDs is 1.5 inches high. How many CDs would be in a stack that is 3.5 inches high?
1.5 33
= 3.5x
1·5x = 33 x 3.5
x
77 CDs=
115.51.5
=
x
4-4 Solving Proportions
Check It Out: Example 2BMaria drives at a constant speed for 3 hours and travels 175 miles. How far would she drive in 4.5 hours at the same speed?
= 4.5x
3x = 175 . 4.5
x
262.5 miles=
787.53
=
x
3175
4-4 Solving Proportions
Standard Lesson Quiz
Lesson Quizzes
Lesson Quiz for Student Response Systems
4-4 Solving Proportions
Lesson Quiz: Part I
Use cross products to solve the proportion.
1. 2520
= 45t
2. x9
= 1957
3. 23
= r36
4. n10
=288
t = 36
x = 3
r = 24
n = 35
4-4 Solving Proportions
Lesson Quiz: Part II
5. Carmen bought 3 pounds of bananas for $1.08. June paid $1.80 for her purchase of bananas. If they paid the same price per pound, how many pounds did June buy?5 pounds
4-4 Solving Proportions
1. Use cross products to solve the proportion.
=
A. t = 16
B. t = 24
C. t = 32
D. t = 36
Lesson Quiz for Student Response Systems
24 16
48 t
4-4 Solving Proportions
2. Use cross products to solve the proportion.
=
A. y = 2
B. y = 4
C. y = 8
D. y = 16
Lesson Quiz for Student Response Systems
y 16
21 84
4-4 Solving Proportions
3. Use cross products to solve the proportion.
=
A. r = 20
B. r = 15
C. r = 10
D. r = 5
Lesson Quiz for Student Response Systems
4 5
r 25
4-4 Solving Proportions
4. Use cross products to solve the proportion.
=
A. n = 21
B. n = 28
C. n = 32
D. n = 36
Lesson Quiz for Student Response Systems
n 16
21 12
4-4 Solving Proportions
5. If you put an object that has a mass of 25 grams on one side of the balance scale, you would have to put 55 paper clips on the other side to balance the weight. How many paper clips would balance the weight of a 30-gram object?
A. 55 paper clips
B. 58 paper clips
C. 60 paper clips
D. 66 paper clips
Lesson Quiz for Student Response Systems