Intermediate Geometry : Plane Geometry

Study concepts, example questions & explanations for Intermediate Geometry

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Example Questions

Example Question #621 : Plane Geometry

Are the two triangles similar? If so, which postulate proves their similarity? (Figure not drawn to scale)

Int_geo_number_4

Possible Answers:

Yes, side-side-side postulate

No, the triangles are not equal

Yes, angle-angle postulate

Yes, side-angle-side postulate

Correct answer:

Yes, angle-angle postulate

Explanation:

The triangles are similar by the angle-angle postulate. 2 corresponding angles are equal to each other, therefore, the triangles must be similar.

Example Question #622 : Plane Geometry

Are the two triangles similar? If so, which postulate proves their similarity? (Figure not drawn to scale)

Int_geo_number_5

Possible Answers:

Yes; angle-angle postulate

Yes; side-angle-side postulate

Yes; side-side-side postulate

No, the triangles are not similar

Correct answer:

No, the triangles are not similar

Explanation:

The triangles are not similar, and it can be proven through the side-angle-side postulate. The SAS postulate states that two sides flanking a corresponding angle must be similar. In this case, the angles are congruent. However, the sides are not similar.

\displaystyle \frac{12}{3}=4

\displaystyle \frac{18}{4}=4.5

\displaystyle 4.5 \neq 4

Example Question #121 : Acute / Obtuse Triangles

Sim._tri._vt_series

If the two triangles shown above are similar, what is the measurements for angles \displaystyle a and \displaystyle b

Possible Answers:

\displaystyle a=75^\circ\displaystyle b=30^\circ 

\displaystyle a=130^\circ\displaystyle b=30^\circ

Not enough information is provided. 

\displaystyle a=37.5^\circ\displaystyle b=15^\circ

Correct answer:

\displaystyle a=75^\circ\displaystyle b=30^\circ 

Explanation:

In order for two triangles to be similar, they must have equivalent interior angles.

Thus, angle \displaystyle a=75 degrees and angle \displaystyle b=30 degrees. 

Example Question #122 : Acute / Obtuse Triangles

Sim._tri._vt_series

Using the similar triangles above, find a possible measurement for sides \displaystyle x and \displaystyle y.

Possible Answers:

\displaystyle y=6 and \displaystyle x=16

\displaystyle y=3 and \displaystyle x=9

\displaystyle y=8 and \displaystyle x=16

\displaystyle y=8 and \displaystyle x=18

Correct answer:

\displaystyle y=6 and \displaystyle x=16

Explanation:

Since the two triangles are similar, each triangles three corresponding sides must have the same ratio.

The original ratio of side lengths is:

\displaystyle 3:8

Thus a similar triangle will have this same ratio: 

\displaystyle 3:8\rightarrow 3\cdot 2:8\cdot2\rightarrow 6:16

Example Question #1 : How To Find If Two Acute / Obtuse Triangles Are Similar

Triangle one and triangle two are similar triangles. Triangle one has two sides with lengths \displaystyle 5 and \displaystyle 7. What are possible measurements for the corresponding sides in triangle two?  

Possible Answers:

\displaystyle 15 and \displaystyle 17

\displaystyle 4 and \displaystyle 6

\displaystyle 15 and \displaystyle 21

\displaystyle 9 and \displaystyle 12

Correct answer:

\displaystyle 15 and \displaystyle 21

Explanation:

Since the two triangles are similar, each triangles three corresponding sides must have the same ratio.

The ratio of side lengths for triangle one is:

\displaystyle 5:7

Thus the ratio of side lengths for the second triangle must following this as well: 

\displaystyle 5:7\rightarrow 5\cdot 3: 7\cdot 3=15:21, because both side lengths in triangle one have been multiplied by a factor of \displaystyle 3

Example Question #3 : How To Find If Two Acute / Obtuse Triangles Are Similar

Triangle one and triangle two are similar triangles. Triangle one has two sides with lengths \displaystyle 6 and \displaystyle 2. What are possible measurements for the corresponding sides in triangle two?

Possible Answers:

\displaystyle 4 and \displaystyle 1

\displaystyle 1 and \displaystyle 4

\displaystyle 18 and \displaystyle 8

\displaystyle 24 and \displaystyle 8

Correct answer:

\displaystyle 24 and \displaystyle 8

Explanation:

Since the two triangles are similar, each triangles three corresponding sides must have the same ratio.

The ratio of triangle one is:

\displaystyle 6:2\rightarrow 3:1


Therefore, looking at the possible solutions we see that one answer has the same ratio as triangle one. 

\displaystyle 3\cdot 8: 1\cdot 8 \rightarrow 24:8=3:1



Example Question #1 : How To Find If Two Acute / Obtuse Triangles Are Similar

Triangle one and triangle two are similar triangles. Triangle one has two sides with lengths \displaystyle 16 and \displaystyle 9. What are possible measurements for the corresponding sides in triangle two?

Possible Answers:

\displaystyle 21 and \displaystyle 34

\displaystyle 34 and \displaystyle 18

\displaystyle 34 and \displaystyle 21

\displaystyle 32 and \displaystyle 18

Correct answer:

\displaystyle 32 and \displaystyle 18

Explanation:

Since the two triangles are similar, each triangles three corresponding sides must have the same ratio. 

The ratio of the side lengths in triangle one is:

\displaystyle 16:9

If we take this ratio and look at the possible solutions we will see:

\displaystyle 16:9=(16\times 2):(9\times 2)

\displaystyle 16:9=32:18

Example Question #6 : How To Find If Two Acute / Obtuse Triangles Are Similar

Triangle one and triangle two are similar triangles. Triangle one has two sides with lengths \displaystyle 23mm and \displaystyle 35mm. What are possible measurements for the corresponding sides in triangle two?

Possible Answers:

\displaystyle 92mm and \displaystyle 140mm

\displaystyle 13mm and \displaystyle 17mm

\displaystyle 21mm and \displaystyle 32mm

\displaystyle 46mm and \displaystyle 65mm

Correct answer:

\displaystyle 92mm and \displaystyle 140mm

Explanation:

Since the two triangles are similar, each triangles three corresponding sides must have the same ratio. 

The ratio of triangle one is:

\displaystyle 23:35

If we look at the possible solutions we will see that ratio that is in triangle one is also seen in the triangle with side lengths as follows:

\displaystyle 23:35=(23\times 4):(35\times 4)=92:140

Example Question #1 : How To Find If Two Acute / Obtuse Triangles Are Similar

Tri_sim_vt_series_cont_

Using the triangle shown above, find possible measurements for the corresponding sides of a similar triangle?

Possible Answers:

\displaystyle 3 and \displaystyle 7

\displaystyle 23 and \displaystyle 46

\displaystyle 5 and \displaystyle 8

\displaystyle 21 and \displaystyle 48

Correct answer:

\displaystyle 21 and \displaystyle 48

Explanation:

Since the two triangles are similar, each triangles three corresponding sides must have the same ratio. 

The ratio of the triangle is:

\displaystyle 7:16

Applying this ratio we are able to find the lengths of a similar triangle.

\displaystyle 7:16=(7\times 3):(16\times3)=21:48

Example Question #623 : Plane Geometry

Tri_sim_vt_series_cont_

Using the triangle shown above, find possible measurements for the corresponding sides of a similar triangle?

Possible Answers:

\displaystyle 145 and \displaystyle 165

\displaystyle 9 and \displaystyle 13

\displaystyle 13 and \displaystyle 19

\displaystyle 200 and \displaystyle 213

Correct answer:

\displaystyle 145 and \displaystyle 165

Explanation:

Since the two triangles are similar, each triangles three corresponding sides must have the same ratio. 

The ratio of the triangle is:

\displaystyle 29:33

Applying this ratio we are able to find the lengths of a similar triangle.

\displaystyle 29:33=(29\times 5):(33\times 5)=145:165

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