Calculate the length of CD give your answer to 3 significant figures.
1 answer:
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Let length = l
width = w
length = 3 times width = 3w
Area of the land = 75 sq. m
Area = length × width = 3w×w = 75
3w²=75
w²=25
w=5 m
length = 3×15 = 15m
Now lets make the figure with the path of width x meters
(Refer the attached figure for easy understanding)
The inner length is the length of the rectangle reduced by x meters on either side due to the path
that is 15-x-x = 15-2x
the inner width is the width reduced by x meters in either side
= 5-x-x = 5-2x
Now lets calculate the inner area = inner length × inner width
(15-2x)×(5-2x)
=
= sq. m
Now the function to calculate the cost
f(x) is given by $3.00 × area of the inner land
f(x) = 3 × {75-40x+4x²)
= 225-120x+12x²
or
= 12x²-120x+225
