Math gurus...help with my daughter's homework

[Fritzo]

It's been 20 years since I took geometery:

If the area of a triangle is 12cm², what would the area be if the length of all the sides were doubled?

(This is 6th grade homework! I didn't do this crap until high school!)

 

[josh0099]

1/2*B*H so if the sides where 6 and 4 to start with....double that 12 * 8 = 96*1/2 = 48cm^2

 

[MikeyIs4Dcats]

if a =4, b=6, then (0.5)ab= (0.5)(4)(6) = 12

if a =8, b=12 then ???

 

[Savij]

right triangle? area = 1/2 base * height (two legs at 90degrees)
double the lengths = 1/2 base*2*height*2
area of double = 2 * base times height = 4*(1/2 base * height)

 

[gorcorps]

Originally posted by: Savij
right triangle? area = 1/2 base * height (two legs at 90degrees)
double the lengths = 1/2 base*2*height*2

that's the area of any triangle, not just right ones

 

[JohnCU]

i almost asked for pics until you said 6th grade

 

[Savij]

Originally posted by: gorcorps

Originally posted by: Savij
right triangle? area = 1/2 base * height (two legs at 90degrees)
double the lengths = 1/2 base*2*height*2

that's the area of any triangle, not just right ones

but it's harder to find height of non-right triangles, right? am i making this too complicated? It's been a while for me too.

 

[Savij]

Originally posted by: JohnCU
i almost asked for pics until you said 6th grade

PICS! Of the triangle.

 

[Fritzo]

So it's just 24? I thought it would have been more difficult

 

[Savij]

Originally posted by: Fritzo
So it's just 24? I thought it would have been more difficult

48?

 

[coldmeat]

Originally posted by: Fritzo
So it's just 24? I thought it would have been more difficult

It's 48...

 

[TwiceOver]

I'm going to dread the day I have to help my kids with math.

 

[josh0099]

Originally posted by: Fritzo
So it's just 24? I thought it would have been more difficult

fail

 

[Fritzo]

Originally posted by: coldmeat

Originally posted by: Fritzo
So it's just 24? I thought it would have been more difficult

It's 48...

Whaaa?


Oh, ok, you're essentially multiplying two numbers by two, or the product by 4. I get it.

 

[Savij]

Originally posted by: Fritzo

Originally posted by: coldmeat

Originally posted by: Fritzo
So it's just 24? I thought it would have been more difficult

It's 48...

Whaaa?


Oh, ok, you're essentially multiplying two numbers by two, or the product by 4. I get it.

Trick: if you multiply the perimeter by x the area multiplies by xsquared and the volume multiplies by xcubed

 

[RESmonkey]

48.

Edit = I confirmed it mathemetically and graphically.

Math way:

grab two numbers outta thin air, plug em in .5bh, get area. Now double those numbers and get area. Area will be 4x original. 12x 4 = 48 WINNAR.



Easy as hell way:

Draw an euqilateral tri. Extend sides. Now it looks like a pyramid with 3 base tri's and one top. Total 4 tris. So 12 x 4 = 48. EPIC WINNAR.

My bad. I used 20 as the area when really 20 is the number of years OP hasn't done math in. lol....

 

[theprodigalrebel]

Area = 0.5 x b x h
If you double all the sides,
Area = 0.5 x 2b x 2h -> 4 x (0.5 x b x h)

The correct answer is 4 times the area = 48 sq. cms.

 

[Agentbolt]

Stupid Geometry! "This is a line. Prove that it is a line" FUCK YOU GEOMETRY.

<----- Barely passed high school geometry

 

[RESmonkey]

Psshh...I never did proofs. I had to take geometry over the summer inorder to take accelerated algebra 2, and the summer geometry was a low-level one. Got a perfect score on both finals...oh yeah!

 

[RapidSnail]

Originally posted by: Agentbolt
Stupid Geometry! "This is a line. Prove that it is a line" FUCK YOU GEOMETRY.

lmao, pretty much...:laugh:

 

[thesurge]

use heron's for a quick and rigorous proof.

 

[Epic Fail]

If you approach this problem graphically, you can easily see you will have 4x the original triangle when you double 2 sides.

 

[GTaudiophile]

I remember complaining back in the day that my parents couldn't help me with math, but now I understand...

Thanks for the ".5bh" walk through memory lane!

 

[RESmonkey]

Originally posted by: Epic Fail
If you approach this problem graphically, you can easily see you will have 4x the original triangle when you double 2 sides.

+1

 

[LordMorpheus]

this is easy. Scaling the dimensions of any 2d object by 2 will up the area by 2^2, so 4. 12*4 = 48 cm2.

Similarly, doubling the sides of a 3d object like a pyramid or box will up the volume by 2^3