Answer:
D
Step-by-step explanation:
For each triangle, you are given two sides and the included angle (the one between those 2 sides). That's side-angle-side, so it is S-A-S.
The SAS Rule for Similar Triangles says that for 2 triangles X and Y, if you have the SAS of one and the SAS of the other, then X and Y are similar (same shape and proportions) if
(a) the angle in X is congruent (same) as the angle in Y
(b) the ratio between the two given sides in X is the same as the ratio between the two given sides in Y
For this particular problem, the ratio PR/PQ = 18/21 = 6/7 if you simplify by dividing both top and bottom by 3.
So we are looking for another triangle where we have the same ratio. (Put the smaller number on top, in the fraction.)
Answer A: 12/15 simplifies to 4/5, wrong answer
Answer B: 9/12 simplifies to 3/4, wrong answer
Answer C: 6/10 simplifies to 3/5, wrong answer
Answer D: 15/17.5 looks harder, because there is a decimal in it. But we know 17.5 is just 17 and a half, so I would first multiply top and bottom by 2
We get 30/35. That looks a lot better. Now it is easier to see we can divide both top and bottom by 5.
We get 6/7! That is the correct answer, so D is the triangle similar to PQR.
Hey so yeah this can be a challenging problem, Vol (V) is much easier to solve than surface area (SA), but I'll show you how it's done, my friend.
First of all, V (prism) = area of base (B) × h
We know that the height (h) of this prism is given, which we'll need later on: h = 5 ft, and area of base (B) is given as 60 ft2
So V = 60 ft2 × 5 ft = 300 ft3
So now for the hard part... how to calculate the SA of this prism
IF YOU DON'T NEED SA FOR THIS TYPE OF PROBLEM, DO NOT PROCEED!!!
[VERY DETAILED]
means solving the dimensions (sides) of that pesky polygon base (B) or lid.
The most important things about polygons are:
1) is it regular (same angle ° and side length)??
2) How many sides or angles??
This has to be regular, because they give you no other info so it has to be, in order to solve. And then it has 5 sides and angles = regular pentagon. ("penta" means 5).
Now there are 360° in any circle, so:
take the central angles of where the sides meet at the center forming triangles (see drawing above), each of those (5) central <'s = 360/5 = 72°
Now the apex of each of these triangles = 72°
but with our 5 triangles, we need to find the height of each triangle -- which is the midpoint of the side (base (b) of triangle), and h is perpendicular to this b. By bisecting that apex angle of 72, it forms 2 equal right triangles of
72/2 = 36°. So each right triangle has 36, 90, and?? 180-36-90 = 90-36 = 54°
let's call the base (b) = 1 side of pentagon
= side (s)
Therefore (see 2nd image drawn above) tangent (tan) of € = opposite/adjacent, or
tan (54) = h÷1/2b --> h = [tan (54)]×(1/2)b
1/2b = h/[tan (54)] = h/1.38
Also the area of each of the larger 5 triangles A(t) = 1/2b×h, and that area A(t) × 5 = area of whole pentagon base A(B)
So now after all that... our A(B) given at beginning = 60ft2. let's put it all together:
1/2b = h/[tan (54)] = h/1.38
A(t) = 1/2b×h, and A(B) = 5×A(t)
which means that A(B) = 5×(1/2b×h)
AND since the other calculation shows that 1/2b = h/1.38, plug that value into the A(B) formula...
.
.
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now that we have height (h) of each triangle, we can go back to our tan equation for the triangle: tan (54) = 1.38 = h/(1/2b)
--> 1/2×b = h/1.38 --> base (b) = 2h/1.38
b = 2(4.06 ft)/1.38 = 8.12 ft/1.38 = 5.90 ft, for which b us also the width of each rectangular side panel (w)
length (l) of these sides was given as height of the whole prism = 5 ft
NOW FINALLY... THE FINAL SURFACE AREA OF THE PRISM (SA) = (2×A(B)) + (5×rectangular side)
SA = (2×60 ft2) + (5×(l×w)) = 120 ft2 + 5×5ft×5.9ft
SA = 120 ft2 + 147.62 ft2 = 267.62 ft2
Using the triangle, we can find the angle lengths and using those and trig ratios, find the side lengths. Lets say the top side length is "y".
Using the Law of triangles, we can find the missing angle from 180-90-70=20 deg.
Then we can use the Law of sines,
sin(70)/13=sin(20)/y
y=sin(20)*13/sin(70)
y=15.34
Finally, we use the Pythagorean Theorem, (13)^2+(15.34)^2=x^2
x = 20.1
The height is: 7.5 inches. Since the terrarium is 14.5 inches in total, and the width is 7 inches, the remaining inches makes up the height and that is 7.5.
