SOLUTION: Persons taking a 30-hour review course to prepare for a standardized exam average a score of 620 on that exam. Persons taking a 70-hour course average a score of 788. Using an equa

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Question 260698: Persons taking a 30-hour review course to prepare for a standardized exam average a score of 620 on that exam. Persons taking a 70-hour course average a score of 788. Using an equation for the line whose graph depicts this data, predict the average score for person taking a 55-hour review course. Round your answer to the tenths place.
Found 2 solutions by drk, richwmiller:
Answer by drk(1908) About Me  (Show Source):
You can put this solution on YOUR website!
we have 2 coordinates here: (30, 620) and (70, 788). We can find the slope using
m+=+%28y2-y1%29%2F%28x2-x1%29
which becomes
m+=+%28788-620%29%2F%2870-30%29
and then
m+=+168%2F40
or
m=+4.2
--
Now, we use our slope and a coordinate to create the equation using
y+=+mx+%2B+b.
we get
620+=+4.2%2A30+=+b
and then
620+=+126+%2B+b
finally
b+=+494
--
now our answer as
y+=+4.2x+%2B+494
--
If you take a 55 hour course, you should get
y+=+4.2%2A55+%2B+494
or
y+=+725

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
We have two points
(30,620)
(70,788)
y-y/x-x=m
788-620/70-30=m
168/40=84/20=42/10=4.2=m
y=4.2x+b
620=4.2*30+b
b=494
y=4.2x+494 equation
y=4.2*55+494=725 predicted score for 55 hours
No need to round.