Anyone Good At Maths? Please Help Me?!

13 replies
Found 4th May 2010
What is the length of the common rafter if the rise is 1.2m and the span is 3.0m?

Use: AB=(Squared)AC2 + CB2

Type in your answer to 3 decimal places

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I thought i was untill i saw this

Original Poster

shosie;8523198

I thought i was untill i saw this



Ha, Same ;-)

shosie;8523198

I thought i was untill i saw this



lol my thoughts exactly

Pythags theorum

AB=(square route of(1.2^2 + 1.5^2))

AB = (square route of (1.44 + 2.25)

AB= (square route of (3.69))

AB = 1.9209372712298546059464653023865

AB = 1.921 (3dp)

You got a diagram? And I think you need to re-type the formula, it's too ambiguous as it is....

think it needs the pythagorus theroy. thats about as far as i can get.

you get the 1.5 from half the span, ie the peak of the roof is going to be at the half way point of the span. Therefore you have a triangle with height 1.2, width 1.5, and the pependictular line petween them is AB, ie the rafter.

Original Poster

ThePasty;8523272

you get the 1.5 from half the span, ie the peak of the roof is going to … you get the 1.5 from half the span, ie the peak of the roof is going to be at the half way point of the span. Therefore you have a triangle with height 1.2, width 1.5, and the pependictular line petween them is AB, ie the rafter.



Are You A Roofer Buy Any Chance? Or A Maths Teacher? You A Genius, Thanks, I Left Some Rep :thumbsup::thumbsup:

AahBisto;8523310

Are You A Roofer Buy Any Chance? Or A Maths Teacher? You A Genius, … Are You A Roofer Buy Any Chance? Or A Maths Teacher? You A Genius, Thanks, I Left Some Rep :thumbsup::thumbsup:



Sadly neither but did degree and love maths. :thumbsup:

Original Poster

ThePasty;8523347

Sadly neither but did degree and love maths. :thumbsup:



Okay, Well Thanks Again, I Will Send You A Message If I Have Any More Questions If Thats Okay?

AahBisto;8523355

Okay, Well Thanks Again, I Will Send You A Message If I Have Any More … Okay, Well Thanks Again, I Will Send You A Message If I Have Any More Questions If Thats Okay?



yeah ok

If the span is 3m across and the height is 1.2m you will need to split the 3m in half to get a smaller triangle so as to obtain the sloping length.
The sloping lengths are therefore (1.5x1.5) + (1.2x1.2) and then squre root this answer.
so 1.5x1.5 = 2.25
1.2x1.2 = 1.44
so sloping beam is square root of 2.25+1.44 = 1.921m.

Hope this helps.

Original Poster

briggsa30;8523542

If the span is 3m across and the height is 1.2m you will need to split … If the span is 3m across and the height is 1.2m you will need to split the 3m in half to get a smaller triangle so as to obtain the sloping length.The sloping lengths are therefore (1.5x1.5) + (1.2x1.2) and then squre root this answer.so 1.5x1.5 = 2.251.2x1.2 = 1.44 so sloping beam is square root of 2.25+1.44 = 1.921m.Hope this helps.




I Did Sort Of Understand That, Thanks
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