Maths help please: area in a quadralateral?

[Oakie]

So I'm doing some landscaping and laying bark in an area at the back of our house.

The shape I'm working with is a quadralateral with end lengths of 2 metres and 5 metres and side lengths of 7.3 metres and 7.8 metres.

A) how many square metres is that?

B) how many cubic metres of bark would it take to fill that area 1cm deep? (it'll be deeper than that but if I have the 1cm calc I can work out 3cm, 5cm etc)

Yes I failed school cert maths. Famously at a post office training course when we had to do a similar exercise but around estimating quantities of paint to paint a room, where others came up with about 17litres, I came up with about 20,000 litres. I of course had filled the room with paint. Consequently when these questions come up, I seek help.

[bogan]

Quantity could vary depending on the angles between them lengths, are any a 90 deg corner?

at your paint calculations

[Zedder]

Multiply the length by the width to get square metres.

For cubic metres just do the same as above but multiply by depth. You must use the same units of measurement all through the equation though ie: Don't use metres for length and width then stay with centimetres for depth. EG: 50cm = 500mm or .5 of a metre.

[yachtie10]

So I'm doing some landscaping and laying bark in an area at the back of our house.

The shape I'm working with is a quadralateral with end lengths of 2 metres and 5 metres and side lengths of 7.3 metres and 7.8 metres.

A) how many square metres is that?

B) how many cubic metres of bark would it take to fill that area 1cm deep? (it'll be deeper than that but if I have the 1cm calc I can work out 3cm, 5cm etc)

Yes I failed school cert maths. Famously at a post office training course when we had to do a similar exercise but around estimating quantities of paint to paint a room, where others came up with about 17litres, I came up with about 20,000 litres. I of course had filled the room with paint. Consequently when these questions come up, I seek help.

rough calc is (2+5/2)*(7.3+7.8/2) to give square metres of 26.25
1 cm deep would be divide by 100 to give cubic metres of .2625 which is the same as 26 litres

only rough as dont know the shape

[slofox]

Approx 25.2 square metres

You'd need about 0.252 cubic metres to cover it to 1cm (1% of the area since 1cm is 1% of a metre.)

This is approximate since my diagram is only roughly to scale...

I think.

[Oakie]

Quantity could vary depending on the angles between them lengths, are any a 90 deg corner?

at your paint calculations

The angles at the ends of the 7.3 metre side are both 90 deg.

[bogan]

The angles at the ends of the 7.3 metre side are both 90 deg.

You sure? doesn't really fit with the 7.8m figure for the opposite side.

[slofox]

So in fact you have a rectangle plus a triangle.

Your rectangle is 7.3 x 2.0 square metres. =14.4 square metres.

Your triangle is 7.3m high and 3m across the base. Area of a triangle is "half the base by perpendicular height". Which is 1.5 x 7.3 metres. =10.95 square metres.

Add 'em together and you have 25.35 square metres.

Cover 1cm deep you need .2535 cubic metres. Or 253.5 litres.

[slofox]

1 cm deep would be divide by 100 to give cubic metres of .2625 which is the same as 26 litres

260 litres? 1000 litres per cubic metre?


Yachtie's calcs and mine are pretty close. Suffice to say that if you bought a cubic metre of bark it would cover to around 4cm deep...

[Oakie]

Multiply the length by the width to get square metres.
.

I could do that bit if it was a rectangle but the odd shape threw me.

I've realised now that as the 7.3m side had 90 degree angles at each end I could have called the shape a rectangle by saying both ends were 5m and then working out the area of that thoeretical shape. I could then deduct the area of the additional triangle I have just added to the original shape to get the true area. Now, where is Excel ...
5m x 7.3m = 36.5m less 7.3m (the length of the side with then 90deg angles) x 3m (the end of the end of the triangle I added to make my odd shape a rectangle) x .5 = 10.95 Now 36.5 - 10.95 = 25.55sqm. Damned close to what you fine gentlemen achieved so I'm happy with that. I now know that a 2 cubic metre trailer load will cover the area to a depth of about 8cm which is more than enough.
Thanks folks!

[Oakie]

So in fact you have a rectangle plus a triangle.

Your rectangle is 7.3 x 2.0 square metres. =14.4 square metres.

Your triangle is 7.3m high and 3m across the base. Area of a triangle is "half the base by perpendicular height". Which is 1.5 x 7.3 metres. =10.95 square metres.

Add 'em together and you have 25.35 square metres.

Cover 1cm deep you need .2535 cubic metres. Or 253.5 litres.

Ha ha. I guess i was working that out as you posted it here. Slightly different method but same answer so it must be right. Cheers!

[Oakie]

You sure? doesn't really fit with the 7.8m figure for the opposite side.

One end was 2 metres, the other was 5 which created the extra length on the other side.

[bogan]

One end was 2 metres, the other was 5 which created the extra length on the other side.

Yeh my head told me that would make it more than 7.8 though. But a calculator tells me it would make 7.9, close enough.

[Oblivion]

I tried calculating it and got 28.25m2 as the area. So thats 0.2825m3 per cm deep.

[Bikemad]

i get 15 ohms................no wait!!