Problem

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Problem 21Direct Variation
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• PRAXIS WI
• Maren Lau Narrator of the Chalk Talk
• Jarod Hart
• Kristin Radermacher
• Chelsea Simon
• Dr. Rebecca LeDocq

2
Trinas paycheck earnings, p, varies directly as
the number of hours, h, she works. If she works
19 hours and earns 187.15, what should she earn
if she worked 40 hours? A. 394.00 B. 44
3.25 C. 472.80 D. 512.20
200
Earnings
16 hrs
Hours Worked
Feedback A Correct Answer! Feedback B This is
the earnings for 45 hours worked. Feedback C
This is the earnings for 48 hours worked.
Feedback D This is the earnings for 52 hours
worked.
Hours Worked Some input value by the reader.
Earnings Multiply the value the reader entered
for Hours Worked by 12.5 and replace the word
Earnings with this value.
p kh
Problem 21 Direct Variation
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Tutorial
In order to solve this problem, we need to figure
out by how much earnings, p, increases as number
of hours worked, h, increases. We can do this by
using this formula
Highlight in bubble to pop-up
p kh, Where k is the ratio of how much earnings
will increase as number of hours worked
increases.

Problem 21 Direct Variation
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Tutorial
First, we need to figure out what this ratio, k,
is. We can do this by replacing p with Trinas
current paycheck earnings, 187.15. We also need
to replace h with Trinas current number of hours
worked, 19 hours.
Highlight in bubble to pop up
187.15 k(19)
Problem 21 Direct Variation
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Tutorial
Now we have a basic algebra problem. To solve
for the ratio, k, we simply need to divide both
sides of our equation by 19.
Highlight in bubble to pop up
187.15 k(19 hrs) 19 hrs 19 hrs
Wait 3 seconds after first bubble comes up,
then highlight the following in a bubble to pop
up
9.85/hr k
Problem 21 Direct Variation
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Tutorial
Now we have our ratio k 9.85/hr. Using thi
s and our previous equation, p kh, we can
finally solve for Trinas paycheck earnings if
she works 40 hours. Simply substitute our k
value and our new h value into the equation.
Highlight in bubble to pop up
p 9.85/hr (40 hrs)
Wait 3 seconds, then highlight the
following in a bubble to pop up
Multiplying through on the left side we get,
p 394.
Problem 21 Direct Variation
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You can use the RecordNarration Feature to
record a draft Audio portion. First, create a
script for what you want to say in a word
program. Then create any figures you will need
for your chalk talk. Finally, record your chalk
talk.
Problem 21 Direct Variation
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A
Kelseys weight loss, w, varies directly as the
number of hours she spends at the gym per week,
h. Last week she spent 4 hours at the gym and
she lost 1.2 pounds. This week she plans to
spend 7 hours at the gym. How many pounds should
she lose this week?
A. 1.2 pounds
C. 7 pounds
B. 2.1 pounds
D. 4 pounds
Feedback A. This is her weight loss for 4 hours
spent at the gym.
Feedback C. Incorrect Answer
Feedback B. Correct Answer!
Feedback D. Incorrect Answer
Problem 21 Direct Variation
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B
Some number, a, is directly proportional to the
product of the square of b and the cube of c.
When b4 and c-2, then a256. If a-108 and
c6, what is b if b must be a positive real
number?
A. -2
C. 1/4
B. 7/8
D. 1/2
Feedback A. Incorrect Answer - b must be a
positive number.
Feedback C. Incorrect Answer
Feedback B. Incorrect Answer
Feedback D. Correct Answer!
Problem 21 Direct Variation
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C
If gas costs 2.75 per gallon, how much will it
cost for 40 gallons of gas?
A. 110.00
C. 40.00
B. 14.55
D. 42.75
Feedback A. Correct Answer!
Feedback C. Incorrect Answer
Feedback B. This is the ratio of 40 gallons to
2.75/gallon.
Feedback D. Incorrect Answer
Problem 21 Direct Variation
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D
If y varies directly to x, which of the following
is a possible equation relating x and y?
A. y 1/x
C. y ax2 bx c
B. y mx b
D. y ax
Feedback A. This shows y varies inversely to x.
Feedback C. Incorrect Answer
Feedback B. Correct Answer!
Feedback D. Incorrect Answer
Problem 21 Direct Variation
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E
Jims score on his math test varies directly as
the number of hours he studies for the test. If
he got a 75 on his test after studying for 12
hours, what grade should he expect to get if he
studies for 14 hours?
A. 100
C. 92
B. 87.5
D. 81.25
Feedback A. This is what he should expect if he
studies for 16 hours.
Feedback C. Incorrect Answer
Feedback D. This is what he should expect if he
studies for 13 hours.
Feedback B. Correct Answer!
Problem 21 Direct Variation
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F
The revenue, R, that a candy store makes during
the year varies directly as the number of pieces
of candy they sell in that year. In 2005, their
revenue was 75,000 and they sold 300,000 pieces
of candy. How many pieces of candy did they sell
in 2006 if their revenue was 77,000?
A. 600,000 pieces
C. 308,000 pieces
B. 302,000 pieces
D. 298,000 pieces
Feedback A. Their revenue would be 150,000 if
they sold this amount.
Feedback C. Correct Answer!
Feedback D. Their revenue would be 74,500 if
they sold this amount.
Feedback B. Their revenue would be 75,500 if
they sold this amount.
Problem 21 Direct Variation
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G
Suppose a persons weight varies directly as his
or her weight. If Jackie weighs 132 lbs and is
64 inches tall, what should Shelbys height be if
she weighs 123.75 lbs?
A. 58 inches
C. 62 inches
B. 60 inches
D. 63 inches
Feedback A. Her weight would be 119.625 lbs at
this height.
Feedback C. Her weight would be 127.875 lbs at
this height.
Feedback B. Correct Answer!
Feedback D. Her weight would be 129.9375 lbs at
this height.
Problem 21 Direct Variation
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H
If L varies directly as the square root of M,
what would be the correct equation relating m and
l?
A. L kM2
C. M kvL
B. L M2
D. L kvM
Feedback A. This shows L varies directly as the
square of M.
Feedback C. This shows M varies directly as the
square root of L.
Feedback B. Incorrect Answer
Feedback D. Correct Answer!
Problem 21 Direct Variation
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I
Type practice problem here (one problem per
page). Make sure you create any graphs or
figures that is needed for your question.
Type answers in text boxes below.
A.
C.
B.
D.
Type feedback for answers in text boxes below.
Feedback for A.
Feedback for C.
Feedback for B.
Feedback for D.
Problem Name
17
J
Type practice problem here (one problem per
page). Make sure you create any graphs or
figures that is needed for your question.
Type answers in text boxes below.
A.
C.
B.
D.
Type feedback for answers in text boxes below.
Feedback for A.
Feedback for C.
Feedback for B.
Feedback for D.
Problem Name