How do you solve word problems by
using inequalities?
For example, you are trying to decide
what cell phone plan to choose. Plan
X charges $30 a month plus $0.02
for every text message. Plan Y
charges $50 for unlimited text
messages. How many text messages
do you need to send in order for the
second plan to be cheaper?
In this lesson you will learn
how to solve word problems
by using inequalities.
A Common Mistake
Writing down the inequality wrong
from the word problem.
<
>
less than
greater than
Let’s Review
Check:
x=9
9>7
3(9) – 5 > 2(9 + 1 )
x
#
3x – 5 > 2(x + 1 )
3x – 5 > 2x + 2
+5
+5
3x > 2x + 7
-2x -2x
x>7
Core Lesson
You are going on a field trip and need to
choose where to go. The zoo costs a $100 fee,
plus $10 per student. The museum costs a $250
fee, plus $5 per student. How many students
need to go on the trip in order for the museum
to be a better deal?
Museum Cost < Zoo Cost
250 + 5s < 100 + 10s
Core Lesson
#
s
250 + 5s < 100 + 10s
-5s
Check:
50 = s
250 < 100 + 5s
-100 -100
150 < 5s
30 < 50
250 + 5(50) < 100 + 10(50)
-5s
30 < s
In this lesson you have
learned how to solve word
problems by solving
inequalities.
Guided Practice
For example, you are trying to decide
what cell phone plan to choose. Plan
X charges $30 a month plus $0.02
for every text message. Plan Y
charges $50 for unlimited text
messages. How many text messages
do you need to send in order for the
second plan to be cheaper?
Guided Practice
30 + 0.02x < 50
Extension Activities
Describe one extension activity here…
Extension Activities
Describe another extension activity here…
Quick Quiz
You are at an amusement park and want to know
what would be a better deal. Buying the unlimited
wristband or paying per ride. It costs $60 for
unlimited or $4 per ride. How many rides would you
need to go on in order for the wristband to be a
better deal?
You are at an amusement park and they two
different refillable souvenir cups. One that costs
$5 and has refills for $2 and the other costs $8
and costs $1 for a refill. How many refills do you
need to get in order for the second one to be a
better deal?