1­3 Day 2 Solving Equations word problems
August 26, 2008
1-3 Day 2 Solving Equations
Objective
Solve problems by writing equations.
Jun 25­7:38 PM
1
1­3 Day 2 Solving Equations word problems
August 26, 2008
Check Skills You'll Need
Solve each equation:
1. 43 ­ 3d = d + 9
2. 6(t ­ 2) = 2(9t ­ 4)
3. 6(n ­ 4) = 3n
4. 12 ­ 3(2w + 1) = 7w ­3(7 + w)
5. 7(a + 1) ­ 3a = 5 + 4(2a ­ 1)
Jun 25­7:46 PM
2
1­3 Day 2 Solving Equations word problems
August 26, 2008
A dog kennel owner has 100 ft. of fencing to enclose a rectangular dog run. She wants it to be 5 times as long as it is wide. Find the dimensions of the dog run.
Step 1: Draw a diagram.
Step 2: Define your variables
Let x = the width
Let 5x = the length
Step 3: Write an equation and solve.
x + 5x + x + 5x = 100
12x = 100
x = 25/3
x = 8 1/3
Therefore 5x = 5(8 1/3) = 41 2/3
Width = 8 1/3 ft.
Length = 41 2/3 ft.
Jun 25­7:53 PM
3
1­3 Day 2 Solving Equations word problems
August 26, 2008
The lengths of the sides of a triangle are in the ratio 3:4:5. The perimeter of the triangle is 18 in. Find the lengths of the sides.
Step 1: Draw a diagram.
Step 2: Define your
Let 3x =
Let 4x =
Let 5x =
variables
length of shortest side
length of the second side
length of the third side
Step 3: Write an equation and solve.
3x + 4x + 5x = 18
12x = 18
x = 3/2
x = 1.5
Therefore 3x = 3(1.5) = 4.5
4x = 4(1.5) = 6
5x = 5(1.5) = 7.5
Jun 25­8:11 PM
4
1­3 Day 2 Solving Equations word problems
August 26, 2008
Radar detected an unidentified plane 5000 miles away, approaching at 700 mi/hr. Fifteen minutes later an interceptor plane was dispatched, traveling at 800 mi/hr. How long did the interceptor take to reach the approaching plane?
Step 1: Understand the question.
distance for interceptor + distance for approaching plane = 5000 mi.
Step 2: Define your variables
t = time in hours for interceptor
t + 0.25 = time in hours for the approaching plane
Step 3: Write an equation and solve.
800t + 700(t + 0.25) = 5000
800t + 700t + 175 = 5000
1500t + 175 = 5000
1500t = 4825
t = 3.217 or 3 hr 13 min
Jun 25­8:36 PM
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1­3 Day 2 Solving Equations word problems
August 26, 2008
HOMEWORK
p. 22
# 29-35, 66a, 68
Jun 25­8:44 PM
6