To indirectly measure the distance across a river, Khalil stands on one side of the river
and uses sight-lines to a landmark on the opposite bank. Khalil draws the diagram
below to show the lengths and angles that he measured. Find PR, the distance across
the river. Round your answer to the nearest foot.
N
RI
185 ft
150 ft
0
275 ft
(Diagram is not to scale.)
ft
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Answer:

To indirectly measure the distance across a river Khalil stands on one side of the river and uses sightlines to a landmark on the opposite bank Khalil draws the class=

Respuesta :

Khalil uses the method of similar triangles to find the distance across the river, [tex]\overline{PR}[/tex]

  • The distance across the river is [tex]\underline{308.\overline 3 \ feet}[/tex]

Reasons:

The distances between the formed the sight-lines are;

[tex]\overline{RB}[/tex] = 185 feet

[tex]\overline{OC}[/tex] = 275 feet

The distance between the point close to the river and the next point further from the river [tex]\overline{RO}[/tex] = 150 feet

In triangles ΔPRB and ΔPOC, we have;

∠PRE = ∠POC = 90° Given

∠PER ≅ ∠PCO By corresponding angle formed between two parallel lines and a common transversal.

∴ ΔPRE is similar to ΔPOC by Angle-Angle, AA, similarity theorem

Which gives;

[tex]\displaystyle \frac{\overline {PR}}{\overline {PO}} = \mathbf{\frac{\overline {RE}}{\overline {OC}}}[/tex]

Let x represent the distance across the river, we have;

[tex]\overline{PR}[/tex] = x

[tex]\overline{PO}[/tex] = 150 + x

Which gives;

[tex]\displaystyle \frac{x}{150 + x} = \frac{185}{275}[/tex]

275·x = 185 × (150 + x) = 27,750 + 185·x

275·x - 185·x = 27,750

90·x = 27,750

[tex]\displaystyle x = \frac{27,750}{90} = \mathbf{308.\overline 3}[/tex]

Therefore, the distance across the river, x = [tex]\mathbf{\overline{PR}}[/tex] = [tex]\underline{308.\overline 3 \ feet}[/tex]

Learn more about similar triangles here

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