Bell work
Class Schedule:
1. Bell work: 5 min
2. HW Discussion: 15 min
3. Lesson 9.6: 25 min
Applying
Systems of
Equations
Wind & Water Problems
Today’s Objective
To use systems of equations to
solve wind and water current
problems.
Distance
•D = r  t where d is
distance, r is rate/speed
and t is time.
• A plane can fly 3750 km in 3 hrs.
with the wind. The same plane takes
5 hrs. to fly that same distance
traveling against the wind. Find the
rate of the plane in still air and the
speed of the wind.
• With the Wind Speed is
• (rate of plane + wind speed)  time in air =
distance
(r + w)3 = 3750
• Against the Wind Speed is
• (rate of plane - wind speed)  time in air =
distance
(r - w)5 = 3750
• Brandi can row at a rate of 6 km/h in
still water. She is going to travel 8
km up the Alafia and then return to
her starting point. The rate of the
current is 2 km/h. How long will each
leg of the trip take? What is Brandi’s
average speed ?
•
With the current 8t = 8
•
Against the current 4t = 8
• UT’s crew can row 30 km down the
Hillsborough river in 3 h, but it takes
them 5 hours to return. What is their
rate in still water? What is the rate of
the current?
• An airplane flies 3000 mi in 4 h, but
takes 5 hours to make the second
flight which is the same distance.
What is the plane’s speed in still air?
What is the speed of the wind?
• Mandi is planning a three hour trip
down the Amazon river and back to
her base camp. She knows that she
can paddle in still water at 3 mi/hr
and the current is moving at 2 mi/hr.
How much time can she spend going
downstream? How far can she go
before turning around?
• James takes his boat 36 km
downstream. He makes it 24 km
back upstream before his engine
dies. Both trips took the same
amount of time. If the current is
flowing 3 km/h, what was the rate of
the boat in still water? How long
before James sells the boat?
Homework 9.6: Wind and Water
Current Problems
–Page 440
•Problems1-9 odd