Download 3.6 Literal Equations and Formulas Literal “letter” equations

Good Morning! 
Please take out the following:
Homework
Warm up sheet
Math notebook
Pencil
Red pen
Warm Up 9/11/13
Currently, you have $60 and your sister has $135. You
decide to save $5 of your allowance each week,
whereas your sister decides to spend her whole
allowance plus $10 each week. How long will it be
before you have as much money as your sister?
1) Write a verbal model for this problem.
2) Assign labels to the verbal model.
3) Write an equation that represents the model.
4) Solve the equation and answer the question.
Warm Up Answer
1) Money you currently have + money you save each
week * time = money sister currently has – extra money
she spends each week * time
2) Money you currently have = 60 (dollars)
Money you save each week = 5 (dollars)
Money sister currently has = 135 (dollars)
Extra money she spends each week = 10 (dollars)
Time = w (weeks)
Warm Up Answer Cont.
3) 60 + 5w = 135 – 10w
4) 60 + 5w = 135 – 10w
+ 10w
+ 10w
60 + 15w = 135
- 60
- 60
15w = 75
15 15
It will take 5 weeks before you have
as much money as your sister.
3.6 Literal Equations
and Formulas
Literal “letter” equations: an
equation that uses more than one
letter as a variable.
D=rt
A=bh
C= d
I=prt
You can solve the equation for any of
the variables.
Practice
For D=rt solve for r
D = rt
t t
D=r
t
Practice
For P=2b + 2h, solve for h
P = 2b + 2h
-2b -2b
P - 2b = 2h
P - 2b = 2h
2
2
P – 2b = h
2
Practice
For I = prt solve for p
(Interest = principle ∙ rate ∙ time)
I = prt
rt rt
I = p
rt
Try these
How long will it take
me to make $50
interest on $350 at
10% interest?
Remember to use
I=prt
I = prt
pr pr
I =t
pr
50____ = t
350 (.10)
50 = t
35
~1.43 years = t
Try these
Solve for y
x = 4y – 16
6
x = 4y – 16
6
6x = 4y – 16
+16
+16
6x + 16 = 4y
4
4
6x + 16 = y
4
Try these
Solve for x
3x + y = 4
3x + y = 4
-y -y
3x = 4 – y
3
3
x=4–y
3
Homework
Page 157 #5-19
Test corrections due tomorrow
Study for fraction quiz tomorrow
Study for chapter 3 test Friday