The answer is: [C]: -0.7, ⅕, 0.35, ⅔ .
________________________________________
Explanation:
_________________________________________
<span>
Note that in this correct Answer choice "C" given, we have the following arrangement of numbers:
_____________________________________________________
</span>→ -0.7, ⅕, 0.35, ⅔ ;
______________________________________
We are asked to find the "Answer choice" (or, perhaps, "Answer choices?") given that show a set of numbers arranged in order from "least to greatest"; that is, starting with a value that is the smallest number in the arrangement, and sequentially progressing, in order from least to greatest, with the largest (greatest) number in the arrangement appearing as the last number in the arrangement.
______________________
Note the EACH of the 4 (four) answer choices given consists of an arrangement with ONLY one negative number, "- 0.7". Only TWO of the answer choices—Choices "B" and "C"—have an arrangement beginning with the number, "-0.7 "; So we can "rule out" the "Answer choices: [A] and [D]".
________________________
Let us examine: Answer choice: [B]: <span>-0.7, 0.35, ⅕, ⅔ ;
</span>_________________________
Note: The fraction, "⅕" = "2/10"; or, write as: 0.2 .
________________________________________
The fraction, "⅔" = 0.6666667 (that is 0.6666... repeating; so we often see a "final decimal point" rounded to "7" at some point.
___________________________________________
Through experience, one will be able to automatically look at these 2 (two) fractions and immediately know their "decimal equivalents".
____________________________________________
Otherwise, one can determine the "decimal form" of these values on a calculator by division:
_________________________
→ ⅕ = 1/5 = 1 ÷ 5 = 0.2
_________________________
→ ⅔ = 2/3 = 2 ÷ 3 = 0.6666666666666667
___________________________________
For Answer choice: [B], we have:
______________________________
→ -0.7, 0.35, ⅕, ⅔ ;
_________________________
→ So, we can "rewrite" the arrangement of "Answer choice [B]" as:
___________________________________________
→ -0.7, 0.35, 0.2, 0.666666667 ;
________________________________
→ And we can see that "Answer choice: [B]" is INCORRECT; because
"0.2" (that is, "⅕"), is LESS THAN "0.35". So, "0.35" should not come BEFORE "⅕" in the arrangement that applies correctly to the problem.
_______________________________________
Let us examine: Answer choice: [C]: -0.7, ⅕, 0.35, 0.666666667 .
____________________________________________
→ Remember from our previous— and aforementioned—examination of "Answer Choice: [B]" ; that:
____________________________
→ ⅕ = 0.2 ; and:
→ ⅔ = 0.666666667
_______________________
So, given:
____________
→ Answer choice: [C]: -0.7, ⅕, 0.35, ⅔ ;
______________________
→ We can "rewrite" this given "arrangement", substituting our known "decimal values for the fractions:
______________________________
→ Answer choice: [C]: -0.7, 0.2, 0.35, 0.666666667 ;
_________________________________________
→ As mentioned above, this sequence starts with "-0.7", which is the ONLY negative number in the sequence; as such, the next positive number is correct. Nonetheless, "0.2" (or, "(⅕") is the next number in the sequence, and is greater than "-0.7". The next number is "0.35. "0.35" is greater than "⅕" (or, "0.2"). Then next number is "(⅔)" (or, "0.666666667").
"(⅔)"; (or, "0.666666667") is greater than 0.35.
____________________________
This set of numbers: "-0.7, ⅕, 0.35, ⅔" ; is arranged in order from least to greatest; which is "Answer choice: [C]: -0.7, ⅕, 0.35, ⅔" ; the correct answer.
________________________________________________________
Answer:
72 feet from the shorter pole
Step-by-step explanation:
The anchor point that minimizes the total wire length is one that divides the distance between the poles in the same proportion as the pole heights. That is, the two created triangles will be similar.
The shorter pole height as a fraction of the total pole height is ...
18/(18+24) = 3/7
so the anchor distance from the shorter pole as a fraction of the total distance between poles will be the same:
d/168 = 3/7
d = 168·(3/7) = 72
The wire should be anchored 72 feet from the 18 ft pole.
_____
<em>Comment on the problem</em>
This is equivalent to asking, "where do I place a mirror on the ground so I can see the top of the other pole by looking in the mirror from the top of one pole?" Such a question is answered by reflecting one pole across the plane of the ground and drawing a straight line from its image location to the top of the other pole. Where the line intersects the plane of the ground is where the mirror (or anchor point) should be placed. The "similar triangle" description above is essentially the same approach.
__
Alternatively, you can write an equation for the length (L) of the wire as a function of the location of the anchor point:
L = √(18²+x²) + √(24² +(168-x)²)
and then differentiate with respect to x and find the value that makes the derivative zero. That seems much more complicated and error-prone, but it gives the same answer.
