Maths

[tooj]

I have a small part of my garden which I would like to cover with coloured aggregate.
It is shaped like a right angled triangle of which the base is 400cms long(13ft), the upright 245 cms (8ft)and the hypotoneuse 460 cms (5ft). Iwould like to fill it 8cms (3inches deep) As you can tell I'm elderly which is why I'm giving both measurements as I don't really understand metric.
Can someone tell me what quanity of aggregate I'll need?

[sandyRoe]

the surface area is 52 square ft. If you wanted 12" deep, you'd need 52 cubic feet. BUt you need a quarter of that (3") 13 cubic feet.

[jim360]

Volume = area of triangle * height = 1/2 * base * upright * depth.

You can plug in the numbers from there.

[sandyRoe]

Wait for confirmation from somebody else here before acting on my answer.

[Prudie]

I've done it in metres. The area is 1/2 x 2.45 x 4 = 4.9 square metres

The volume of aggregate then is 4.9 x 0.08 = 0.392 cubic metres

If they sell it in litres that's 392 litres.

[elliemay1]

Agree with Sandy. (Half the base x perpendicular ht x depth.)

[factor-fiction]

Do you mean 15feet for the hypotenuse rather than 5 ft?

[New Judge]

The area of your triangle is (base x height x 0.5) which equals 13 x 8 x 0.5 = 52. You want to fill that area with 0.25 ft of aggregate so you need 13 cubic feet. Or very slightly under half a cubic yard (a cubic yard is 27 cu. ft.).

The same calculation using your metric measurements is 400 x 245 x 0.5 x 8 which comes to 392 litres or 0.392 of a cubic metre.

[New Judge]

Yes the length ofd the hypotenuse would be approximately 15 feet but it is not needed for this calculation.

[jomifl]

I agree with Sandy, (first time this year?)

[elliemay1]

Hypotenuse would be just over 15 feet, factor fiction, but don't need to know the hypotenuse to calculate amount required.

[The Builder]

Tooj, you'll need around 650 - 700 kg, depending on how much you may lose in the base (which I guess isn't rolled).

"Dumpy" bags contain around 800 - 850 kg. It varies slightly between merchants. They're the big ones that are craned off the back of a truck.

Alternatively, it's usually available in 25kg plastic bags..... of which you'll need 25 - 30. That way would probably work out at more than the cost of a dumpy bag, even with the bit left over.

[tooj]

Thanks for all the advice. I'm still a bit confused. Is 13 cu.ft the same as 392litres, the same as 850kg.

[The Builder]

Almost, Tooj ............

13 cu ft = (roughly) 370 litres = 650 kg

[heathfield]

Forget about triangles for a minute. The base x the upright wiil give the area for a rectangle. Divide the answer by two to get the size of your triangle. Then do the same here to see what quantity you'd need (it's for gravel, but will be hardly any different for aggregate)...

http://www.gravelmaster.co.uk/GravelMasterCalculator.aspx

[heathfield]

Just looked at those figures you give. How can the base be longer than the hypoteneus?

[factor-fiction]

>Hypotenuse would be just over 15 feet, factor fiction, but don't need to know the hypotenuse to calculate amount required

Yes, I realise the hypotenuse isn't relevant to the calculation, but I wondered if the other measurements may be wrong since the other sides have to be less than the hypotenuse (as heathfield has now said0

[Prudie]

did you factor, did you realise??? LOL

[elliemay1]

Hope you manage to get it sorted, tooj. Let us know how you get on.