### Brain Teasers

# Area of a Triangle

What is the area of a triangle with sides 1, 3, and 4 inches?

### Hint

You don`t need a formula to figure this out.### Answer

It`s impossible to have a triangle with those sides. The sum of two of the sides is equal to the third side. The result would be a straight line, and the area would be zero.Hide Hint Show Hint Hide Answer Show Answer

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## Comments

This is assuming planar geometry... but yeah, fair call.

I don't understand why it is not possible?

Check out my plane sketch.

It is 3.3, but rotate the 1 inch line a bit and it would be 3.0 (MS Paint it difficult to manage line lenghts).

http://img220.exs.cx/img220/9486/plane2zn.png

Check out my plane sketch.

It is 3.3, but rotate the 1 inch line a bit and it would be 3.0 (MS Paint it difficult to manage line lenghts).

http://img220.exs.cx/img220/9486/plane2zn.png

Um, I didn't think that there was enough info in that to get that answer (0).

Oh, well.

Oh, well.

i kinda got it, but i feel just so stupid today, i don't thinki could get any of them!!

technically, there is a formula involved. you need to know that 2 sides can't equal the third, and this should probably go in the trick section.

SO EASY, SO ELEMENTARY,

VERGOGNA

VERGOGNA

I couldn't get it...the "open calcualtor" tricked me (sort of)

Good teaser.

Good one. I really had to think about this one, as to why it can't work. BTW, Stephanie's comment that there is a formula involved is not true. You don't need any formula at all, just visualization.

Good job!

Good job!

That was easy, but it might be harder for some1 who didn't know that rule.

I liked this one, thanks great teaser

SMARTY PANTS!

Thats really clever

I got this one....but I do think it goes in the Trick section.....

very clever

very clever

very easy.. i got it right..

i cant believe i missed that!

first angle =0

second angle =0

third angle = 180.

There is a triangle, and its area is zero.

second angle =0

third angle = 180.

There is a triangle, and its area is zero.

thanks.

Ahhhhh nooooo this one got me, I can't believe it!

I actually worked through a bunch of things... might've 'accidentally' ignored some negative signs under square roots, and got 3.35 sq in somehow... then I looked at the hint, got puzzled, didn't bother to rethink it....

bleh. I'd better go give my math minor back or something.

I actually worked through a bunch of things... might've 'accidentally' ignored some negative signs under square roots, and got 3.35 sq in somehow... then I looked at the hint, got puzzled, didn't bother to rethink it....

bleh. I'd better go give my math minor back or something.

This is not a math teaser. It is a trick teaser with math as the subject. Could have been in question form and used for teaser.

cant believe i missed that...

i was thinking of the cosine rule:

a^2 = b^2 + c^2 - 2bc cos A

and then once u get angle... well then u use area = (1/2)ab sin C

well yeah thats what i thought

i was thinking of the cosine rule:

a^2 = b^2 + c^2 - 2bc cos A

and then once u get angle... well then u use area = (1/2)ab sin C

well yeah thats what i thought

[technically, there is a formula involved. you need to know that 2 sides can't equal the third, and this should probably go in the trick section.]

There is no formula involved. Somebody already pointed out you don't need formula, you just need your mind's eye.. 2 sides actually can equal the 3rd side. It's called the pythagorean theorum.

There is no formula involved. Somebody already pointed out you don't need formula, you just need your mind's eye.. 2 sides actually can equal the 3rd side. It's called the pythagorean theorum.

easy

Um, no. Pythagoras would have nothing to do with this one!

Fun quiz, almost got me!

Fun quiz, almost got me!

An interesting one. I think this triangle [180deg, 0deg, 0deg] fits all the basic rules about triangles - it consists of three points in a plane, the internal angles add up to 180deg, the external angles add up to 360deg, and each external angle is equal to the two opposite internal angles. So the answer should be zero, and it's not a trick.

I looked that up, btw, to make sure there weren't any rules about triangles it was breaking

I reread it just to make sure since I read the numbers correctly since it was immediately obvious it wasn't a triangle. Definitely belongs in the trick category.

And to leftclick: a triangle is defined by three NON-COLINEAR points. That means they can't all be on the same point, so it's not a triangle.

And to leftclick: a triangle is defined by three NON-COLINEAR points. That means they can't all be on the same point, so it's not a triangle.

Uh, mistyped: not only can't they all be on the same point, they can't all be on the same line either.

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