A student who is 5 1/4 feet tall has a shadow that is 2 feet and 10 1/2 inches long. At the same time. a flag pole has a shadow that is 10 1/2 feel long. How tall, to the nearest inch, is the flag pole?

Respuesta :

Answer:

The height of the flag pole is approximately 19 feet and 2 inches.

Step-by-step explanation:

Let suppose that length of the shadow of the object is directly proportional to its height. Hence:

[tex]l \propto h[/tex]

[tex]l = k\cdot h[/tex]

Where:

[tex]h[/tex] - Height of the object, measured in inches.

[tex]l[/tex] - Shadow length of the object, measured in inches.

[tex]k[/tex] - Proportionality constant, dimensionless.

Now, let is find the value of the proportionality constant: ([tex]h = 5\,\frac{1}{4} \,ft[/tex] and [tex]l = 2\,ft\,\,10\,\frac{1}{2}\,in[/tex])

[tex]h = \frac{21}{4}\,ft[/tex]

[tex]h = \left(\frac{21}{4}\,ft \right)\cdot \left(12\,\frac{in}{ft} \right)[/tex]

[tex]h = 63\,in[/tex]

[tex]l = (2\,ft)\cdot \left(12\,\frac{in}{ft} \right) + \frac{21}{2}\,in[/tex]

[tex]l = 24\,in + \frac{21}{2}\,in[/tex]

[tex]l = \frac{48}{2}\,in+\frac{21}{2}\,in[/tex]

[tex]l = \frac{69}{2}\,in[/tex]

Then,

[tex]k = \frac{l}{h}[/tex]

[tex]k = \frac{\frac{69}{2}\,in }{63\,in}[/tex]

[tex]k = \frac{69}{126}[/tex]

[tex]k = \frac{23}{42}[/tex]

The equation is represented by [tex]l = \frac{23}{42}\cdot h[/tex]. If [tex]l = 10\,\frac{1}{2}\,ft[/tex], then:

[tex]l = \frac{21}{2}\,ft[/tex]

[tex]l = \left(\frac{21}{2}\,ft \right)\cdot \left(12\,\frac{in}{ft} \right)[/tex]

[tex]l = 126\,in[/tex]

The height of the flag pole is: ([tex]l = 126\,in[/tex], [tex]k = \frac{23}{42}[/tex])

[tex]h = \frac{l}{k}[/tex]

[tex]h = \frac{126\,in}{\frac{23}{42} }[/tex]

[tex]h = \frac{5292}{23}\,in[/tex]

[tex]h = 230\,\frac{2}{23}\,in[/tex]

[tex]h = \frac{115}{6}\,ft\,\frac{2}{23}\,in[/tex]

[tex]h = 19\,\frac{1}{6}\,ft \,\frac{2}{23}\,in[/tex]

[tex]h = 19\,ft\,\,2\,\frac{2}{23}\,in[/tex]

[tex]h = 19\,ft\,\,2\,in[/tex]

The height of the flag pole is approximately 19 feet and 2 inches.