Evaluate 12.3p+11.5r when p=6 and r=7. 12.3(___)+11.5(___) = ___+80.5 = __
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Answer:
The height of the arch at its center is 250/9 or about 27.78 feet.
Step-by-step explanation:
We can write an equation to model the parabolic arch.
Let the left-most point of the arch be the origin (0, 0).
Since the bridge has a span of 100 feet, the right-most point must be (0, 100).
We can use the factored form of a quadratic:
Where <em>p</em> and <em>q</em> are the <em>x-</em>intercepts.
Our <em>x-</em>intercepts are <em>x </em>= 0 and <em>x </em>= 100. Hence:
At a point 40 feet from the center, the height of the arch is 10 feet.
The center is <em>x</em> = 50. So, a point 40 feet from the center can be either <em>x</em> = 10 or <em>x</em> = 90.
So, for instance, when <em>x</em> = 10, <em>y</em> = 10. Substitute and solve for <em>a: </em>
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So:
The same value will result if we let <em>x</em> = 90 and <em>y</em> = 10.
Hence, our equation is:
The height of the arch at its center will be when <em>x</em> = 50. Hence: