Day Two of 7.3

Solve:

4 2 2 114 11

5 5 5 5x y y x

KAYAKING

EXAMPLE 4 Write and solve a linear system

During a kayaking trip, a kayaker travels 12 miles upstream (against the current) and 12 miles downstream (with the current), as shown.The speed of the current remained constant during the trip. Find the average speed of the kayak in still water and the speed of the current.

P. 446 in book

EXAMPLE 4 Write and solve a linear system

STEP 1

Write a system of equations. First find the speed of the kayak going upstream and the speed of the kayak going downstream.

Upstream: d = rt

12 = r 3

4 = r

Downstream: d = rt

12 = r 2

6 = r

EXAMPLE 4 Write and solve a linear system

Use the speeds to write a linear system. Let x be the average speed of the kayak in still water, and let y be the speed of the current.

x y 4=–

Equation 1: Going upstream

EXAMPLE 4 Write and solve a linear system

Equation 2: Going downstream

x y 6=+

EXAMPLE 4 Write and solve a linear system

STEP 2

Solve the system of equations.

x – y= 4

2x = 10

x = 5

Write Equation 1.

Write Equation 2.

Add equations.

Solve for x.

Substitute 5 for x in Equation 2 and solve for y.

x + y = 6

EXAMPLE 4 Write and solve a linear system

5 + y = 6

y = 1

Substitute 5 for x in Equation 2.

Subtract 5 from each side.

Rectangle: P = 24 ft

Twice the length is equal to one less than three times the width.

Find the l & w

• #40 set up for today – oil change

Assignment: P. 448 24-27, 35, 39-40

#42 (A-only) EC – with work

Quiz on tomorrow over 7.1 – 7.3 STUDY!!!