SOLUTION: <center> ECOLOGY The water level of a reservoir is at 27 feet. During a drought the <br> water level falls by 1 1/2 feet per week. Write an equation for the<br> wataer level L

Algebra ->  Graphs -> SOLUTION: <center> ECOLOGY The water level of a reservoir is at 27 feet. During a drought the <br> water level falls by 1 1/2 feet per week. Write an equation for the<br> wataer level L       Log On


   

Question 119052This question is from textbook Algebra 1
:

ECOLOGY The water level of a reservoir is at 27 feet. During a drought the
water level falls by 1 1/2 feet per week. Write an equation for the
wataer level L after w weeks. Graph the equation. In how many weeks will the
water level be at 18 feet.


I tried making a table and using point slope form, but I am just stuck on what to do and my math book isn't exactly explaining it to me. This question is from textbook Algebra 1

Answer by tutorcecilia(2152) About Me  (Show Source):
You can put this solution on YOUR website!
The starting point or y-intercept is 27 feet. The slope is -1 1/2 or -3/2 feet. The slope is negative since the water level is falling. The y-value is the number of feet at a particular week. The x-value = the number of weeks.
.
Using the slope-intercept form of a line: y=mx+b
The equation of this line is: y=%28%28-3%2F2%29x%2B27%29
.
Let y=18 feet
18=%28%28-3%2F2%29x%2B27%29 [solve for the x=value]
x=6 weeks
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So within 6 weeks, the water level will at 18 feet.
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