Transcript • Round-Trip Travel Sarah drives into the city to buy a software program at a computer store.

•
Round-Trip
Travel
Sarah drives into the city to buy a software program at a computer
store. Because of traffic conditions, she averages only 15 mi/h. On
her drive home she averages 35 mi/h. If the total travel time is 2
hours, how long does it take her to drive to the computer store?
• Define: Let t = time of Sarah’s drive to the computer store.
2 – t = time of Sarah’s drive home.
• Relate:
Part of
Sarah’s
travel
To the
computer
store
Return
home
Rate
Time
15
t
35
2–t
Distance
15t
35(2 – t)
Round-Trip Travel
• Write:
15t = 35(2 – t)
15t = 70 – 35t
+35t
+ 35t
50t = 70
t = 1.4
It took Sarah 1.4 h to drive to the computer store.
•
Opposite-Direction
Travel
Jane and Peter leave their home traveling in opposite directions on a
straight road. Peter drives 15 mi/h faster than Jane. After 3 hours,
they are 225 miles apart. Find Peter’s rate and Jane’s rate.
• Define: Let r = Jane’s rate
Then r + 15 = Peter’s rate
• Relate:
Person
Rate
Time
Distance
Jane
r
3
3r
Peter
r + 15
3
3(r + 15)
Opposite-Direction Travel
• Write:
3r + 3(r + 15) = 225
3r + 3r + 45 = 225
6r + 45 = 225
- 45 - 45
6r = 180
r = 30
Jane’s rate is 30 mi/h and Peter’s rate is 15 mi/h
faster, which is 45 mi/h.
More Practice!!!
• Textbook – p. 108 #10 – 14 even, p. 109
#20 – 26 even.
• Homework – Worksheet 2.5