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Ivahew [28]
3 years ago
14

The 3 by 3 grid below shows nine 1 cm × 1 cm squares and uses 24 cm of wire. What length of wire is required for a similar 20 by

20 grid?

Mathematics
1 answer:
Nady [450]3 years ago
5 0

Answer:

840

Step-by-step explanation:

Hi there!

Usually, this kind of problem asks us the perimeter rather than the area. But when talking on this grid on how many cms are necessary to construct one made up of 9 squares 1cm x1 cm. We need to check one thing: Some line segments will be used twice. So this is not a classical perimeter question.

1) So we either manually and carefully count it avoiding not doing it twice the same common line segments.

Or.

2) By just applying an algorithm, Where n is the <em>nxn</em> grid

n(n+1)+n(n+1)=Length \:of \:the \:wire

So, for the 20x20 grid

20(20+1)+20(20+1)=length\\\\20(21)+20(21)=length\\length=840 cm

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Answer:

The integral for the arc of length is:

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By using Simpon’s rule we get: 1.5355453

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Explanation:

The formula for the length of arc of the function f(x) in the interval [a,b] is:

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We need the derivative of the function:

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\displaystyle\int_1^3\sqrt{1+\frac{1}{x^2}}dx

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\displaystyle\int_a^b g(x)}dx\approx\frac{\Delta x}{3}\left( g(a)+4g(a+\Delta x)+2g(a+2\Delta x) +4g(a+3\Delta x)+g(b) \right)

In this problem:

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So, the Simposn’s rule formula becomes:

\displaystyle\int_1^3\sqrt{1+\frac{1}{x^2}}dx\\\approx \frac{\frac{1}{3}}{3}\left( \sqrt{1+\frac{1}{1^2}} +4\sqrt{1+\frac{1}{\left(1+\frac{1}{2}\right)^2}} +2\sqrt{1+\frac{1}{\left(1+\frac{2}{2}\right)^2}} +4\sqrt{1+\frac{1}{\left(1+\frac{3}{2}\right)^2}} +\sqrt{1+\frac{1}{3^2}} \right)

Then simplifying a bit:

\displaystyle\int_1^3\sqrt{1+\frac{1}{x^2}}dx \approx \frac{1}{9}\left( \sqrt{1+\frac{1}{1^2}} +4\sqrt{1+\frac{1}{\left(\frac{3}{2}\right)^2}} +2\sqrt{1+\frac{1}{\left(2\right)^2}} +4\sqrt{1+\frac{1}{\left(\frac{5}{2}\right)^2}} +\sqrt{1+\frac{1}{3^2}} \right)

Then we just do those computations and we finally get the approximation via Simposn's rule:

\displaystyle\int_1^3\sqrt{1+\frac{1}{x^2}}dx\approx 1.5355453

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