isosceles triangle
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isosceles triangle
can anyone help to solve this problem?
In an isosceles triangle, twice one of the angles is 5 times as big as another. What is not a possible size for one of the angles?
The options are 100, 75,40,30,20
In an isosceles triangle, twice one of the angles is 5 times as big as another. What is not a possible size for one of the angles?
The options are 100, 75,40,30,20
Re: isosceles triangle
In an isosceles triangle 2 of the angles are the same.
You can use this fact and trial and error.
Also you cannot exceed the maximum number of degrees in a triangle.
You can use this fact and trial and error.
Also you cannot exceed the maximum number of degrees in a triangle.
Re: isosceles triangle
Here the answer is 20 apparently
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Re: isosceles triangle
and using algebra...
If,
x = the size of one of the equal pair of angles.
y = the third angle.
We have two sets of equations (possibilities):
2x = 5y
2x + y = 180
OR
2y = 5x
2x + y = 180
Solving first pair, we get
x = 75
y = 30
Solving second pair, we get
x = 100
y = 40
Hence, the remaining i.e 20, must be the answer.
If,
x = the size of one of the equal pair of angles.
y = the third angle.
We have two sets of equations (possibilities):
2x = 5y
2x + y = 180
OR
2y = 5x
2x + y = 180
Solving first pair, we get
x = 75
y = 30
Solving second pair, we get
x = 100
y = 40
Hence, the remaining i.e 20, must be the answer.
Re: isosceles triangle
target 2016 - Algebra makes this harder and is not appropriate for this question.
SImple trial and improvement gets the answer in a few seconds.
SImple trial and improvement gets the answer in a few seconds.
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- Posts: 60
- Joined: Sun Oct 19, 2014 12:52 pm
Re: isosceles triangle
It's a matter of choice. There is no one way, but this way makes it show how we arrived at the answer better. Personally I don't like "trial and error"... takes me ages!
Re: isosceles triangle
As mathematicians we judge the best method as the shortest and most elegant - the choice of x and y also makes it harder to remember which variable is which. Note I said trial and improvement - not error!
e = equal angle would have been a better choice.
e = equal angle would have been a better choice.
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- Posts: 60
- Joined: Sun Oct 19, 2014 12:52 pm
Re: isosceles triangle
Now that's getting pedantic. Like I said - it's a matter of choice
Re: isosceles triangle
I would expect most children in y5/6 to solve it without algebra.
Agree trial and improvement, rather than error
Agree trial and improvement, rather than error