Math Is Fun Forum

lisathedork

Member

Registered: 2013-10-24

Posts: 36

Triangles

Hello, I was just wondering about these two questions and making sure they were correct. If not, please explain. 

13. I have a triangle with sides of 3, 4, and 5, and angles of 30o and 60o. Which of the following would be congruent to it? (You will need to use what you've learned about triangles and angle / side relations, as well as your knowledge of the rules of congruence to fill in the gaps and answer the question. Sketches may be helpful.) Give the reasoning or show your work to support your choice:

A. a triangle with angles of 30o, 60o, and 90o
B. an angle of 90o
C.a triangle with sides of 6, 8, and 10
D. a triangle with sides of 3 and 4
E. a triangle with a side measuring 4, next an angle of 90o, and next a side measuring 3
F. a triangle with a  side measuring 3, next an angle of 60o, and next a side measuring 4

The answer I got for this problem is A.
.

14. I have a triangle with sides of 1 and a side of SQRT(2), with an angle of 45o and an angle of 90o. Which of the following would be congruent to it? (You will need to use what you've learned about triangles and angle / side relations, as well as your knowledge of the rules of congruence to fill in the gaps and answer the question. Sketches may be helpful.). Give the reasoning or show your work to support your choice

A. a triangle with a side of 1, then an angle of 90o, and a side of 1
B. a triangle with a side of 1, then an angle of 90o, then a side of SQRT(2)
C.a triangle with the angles 45o, 45o, 90o
D. a triangle with sides of 1 and 1
E. a triangle with a side of 1, then an angle of 45o, then a side of 1
F. a triangle with an angle of 90o, then a side of SQRT(2), then an angle of 45o

The answer I got for this problem is C.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Triangles

Hi;

13) Is not correct.

14) Is not correct.

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

Re: Triangles

hi lisathedork

Let me guess.  These questions came from CompuHigh ???

If so, I'll ignore the fact that a triangle with sides 3, 4, and 5 would have angles of 37, 53 and 90 not 30, 60 , 90, because that's not what they are trying to assess.

Your answer of A for Q.13:  To be congruent the triangles have to be the same size with the same angles.  Answer A does not give any lengths so we don't know enough to choose A.

Maybe B ?  No.  We hardly know anything about this.  We're not even told that it's part of a triangle.

Maybe C ?  This triangle has all lengths double the given one so it's not congruent.  (like answer A, it is a 'similar' triangle)

Maybe D ?  Not enough information.  The third side might be 6.

Maybe E ?  The longest side has to be opposite the largest angle ... maybe 5 opposite 90.  Looks hopeful.  But will the third side be 5 ?  Have they taught you Pythagoras' theorem yet.  If so you can work out the third side ( =   √(3^2 + 4^2) = √25 = 5.)  If you don't know the theorem you could make an accurate drawing.  So this seems to be the best candidate.

Maybe F ? The 60 is in the wrong place.  If it's between the given sides then the third side is definitely not 5. (Try drawing it)

So go for answer E.

Q14.  Your answer is wrong for the same reason as above.  So perhaps you can re-think this one for yourself. It is definitely worth trying to draw each one.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

lisathedork

Member

Registered: 2013-10-24

Posts: 36

Re: Triangles

Thank you for the feedback and yes the questions came from CompuHigh.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Triangles

What are your new answers?

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

lisathedork

Member

Registered: 2013-10-24

Posts: 36

Re: Triangles

Here are my new answers.

13. E

14. A

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Triangles

That looks good. Did you draw them?

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

lisathedork

Member

Registered: 2013-10-24

Posts: 36

Re: Triangles

Yes I did, it pretty much help me with the questions.