1. Objective - To solve word problems involving linear situations.
Three types of word problems
1) Point/Slope
2) Two Points
3) Two Things and a Total

2. Point - Slope Problem A water tank contains 600 gallons of water
and is leaking at a rate of 15 gal/min. Write
a linear equation representing the tank volume
in terms of time.
Let x = # minutes
Let y = volume in gallons

3. Two Points
The volume in a water tank after 10 minutes
is 450 gallons. After 30 minutes, the volume
in the tank is 150 gallons. Write an equation
representing the volume in terms of time.
Let x = # minutes
Let y = volume in gallons

4. Two Things and a Total Sandwiches cost $3 each and sodas cost $2
each. If Sam spent a total of $24, how many
of each could he have bought?
Let x = # of sandwiches
Let y = # of sodas

5. Write a linear equation to describe each situation.
Point and Slope
Two Points
A sky diver jumps from a
plane at 11,000 ft. above the
ground and descends at
15 ft./sec.
A sky diver jumps from a
plane. He is 10,100 ft. above
the ground after 60 sec. and
is 8300 ft. after 3 min.
y = height (ft.)
x = time (sec.)
Start Value =
b =
11,000
Change =
m =
-15

6. Change in price = $0.80/ brick y = 0.80x + b m = 0.80
A masonry company charges $0.80 a brick. The
company will charge $465 for 500 bricks to be
delivered to a site. If x = the number of bricks, and
y = total cost, write an equation for y in terms of x.
Slope
y = mx + b
Change in price = $0.80/ brick
y = 0.80x + b
m = 0.80
465 = 0.8(500) + b
465 = b
Point
500 bricks cost $465
65 = b
(x, y) = (500, 465)
y = 0.8x + 65

7. -3.95 -3.95 Suppose a 5 minute call costs $6.20 and a
20 minute call costs $ Write an equation
which describes cost y in terms of x minutes.
(minutes, cost)
(x, y)
(5, 6.20) (20, 18.05)
y = mx + b
y2- y1
y = 0.79x + b
m = =
x2- x1
20 - 5
6.20 = 0.79(5) + b
11.85
m = =
0.79
6.20 = b 15
2.25 = b
y = 0.79x

8. Let p = # of pens purchased Let r = # of rulers purchased 3p + 1r = 12
Pens cost $3 each and rulers cost $1 each. If Jim spends $12, how many of each did he buy?
Let p = # of pens purchased
Let r = # of rulers purchased
3p + 1r = 12 12 10 8 6 4 2
-3p p
1r = -3p +12
# Rulers
r = -3p +12
m = -3
b = 12
# Pens