today’s date: 11/15/11 “work” word problems notes on handout
TRANSCRIPT
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Today’s Date:
11/15/11
“Work” Word Problems
Notes on Handout
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“Work” Equation
Together + Together = 1
Alone Alone
Always “together Over alone + together Over alone”
Always equals 1
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Ex 1) Nora needs 3 hours to chop down the tree in front of her house. Her younger brother needs 6 hours to do the same job.
How much time would it take them if they worked together?
Nora’s Part of Job
Bro’s Part of Job
1 Whole Job Completed
+ =
3
x
6
x 1
2 6x x
(2) (1)(6)
Multiply every term to get the common denominator
3 6x 2x
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Example 1 cont…
a) Define variable:
b) Write the equation:
c) Solve:
13 6
x x
x is time together
2 hours (to complete the job together)
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T.O.O. SET-UP #3
Do NOT finish the problem.This time they give Sean’s time & time together, but not Ian’s time.
3.5 3.51
6 x
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Example 2 (#4 on WS)
An inlet pipe can fill a tank in 3 hours. It takes 11 hours for the drainpipe to empty the tank. How long will it take to fill the tank if both the inlet pipe and the drainpipe are open?
=Inlet and Drain pipe are working against each other.So, make Drain pipe’s rate alone negative.
3
x
11
x 1
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Example 2 cont…
13 11
x x
11 3 33
8 33
4.125 hours
x x
x
x
(11) (3)(33)
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Example 3 (#5 on WS)
Crane A can unload the container ship in 10 hours, and crane B can unload it in 14 hours. Crane A started to unload the ship at noon and was joined by crane B at 2 pm. At what time was the unloading job of the ship completed?
Crane A: Started at noon (12:00)Crane B: Started at 2:00 Let x = Crane B’s timeCrane A worked 2 hours more than Crane B : x + 2
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Example 3 cont…
21
10 14
x x
Once you get x, you need to add that time to 2:00 to get “WHAT TIME” job was finished.
Finish for HW. Your answer will be a decimal so round to the nearest tenth and convert to “Time”
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T.O.O.
Work with a neighbor to set up #6.Do NOT finish the problem.
Clue: Larger Pump’s time is x – 7
12 121
7x x
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Homework
#8 Finish “Work” Problems side of WS
a) Define Variable
b) Write equation
c) Solve
Products & Quotients; Sums & Differences side: do Every Other Odd
(1, 5, 9, 13, 17, 21)