Calculation

[schiehallion]

Hello all
I have been set a task of calculating the weight of a solid steel cylinder and my answer seems wrong compared to others . the cylinder is 1.4 meters dia. and 12 meters long the density of the steel is 7.85t
I calculated as below
Pie 3.142 x 0.7 x12 = 26.3928 26.3928 x 7.85 = 207,183 tons
but others get.
3.142 x 0.7 x 12 =18.47 18.47 x 7.85 = 145 tons
the 145 ton weight seems to tally with most other online calculating tools what am i doing wrong
Thanks in advance

[Gizmonster]

You're missing a 0.7:

The calculation should be:
3.142 x 0.7 x 0.7 x 12 x 7.85 = 145 tonnes

[Captain2]

Agree with Giz

Volume = Pie x R squared X height/length

[gingejbee]

...because the volume of a cylinder is Pi x radius squared x length...

[Buenchico]

The area of the circular end is Pi times the radius SQUARED = 3.14 x 0.7 x 0.7.

The volume of the cylinder is the area of the end multiplied by its length = 3.14 x 0.7 x 0.7 x 12.

The mass of the cylinder equals its volume times its density = 3.14 x 0.7 x 0.7 x 12 x 7.85 = 145 tonnes.

So you've made TWO errors:
Firstly, you forgot to square the radius when finding the area of a circle.
Secondly, you've failed to check the 'reasonableness' of the second part of your calculation. You shouldn't need a calculator to realise that 26-and-a-bit multiplied by 7-and-a-bit can't come anywhere close to over 200,000!

[schiehallion]

Ahh got it now Thank you Giz and others much appreciated

[Gizmonster]

I assumed that when the OP just made a typo when they wrote 207,183 and that they meant to write 207.183

[Gizmonster]

That last post doesn't make much sense, it's meant to say:

I assumed that the OP just made a typo when they wrote 207,183 and that they meant to write 207.183

[schiehallion]

Yes giz it was a typo 207 tons.
Thanks again for all your answers

[beso]

Gizmonster //I assumed that the OP just made a typo when they wrote 207,183 and that they meant to write 207.183//

Be careful with such assumptions. There are many regions, particularly in Europe, where the decimal character is the comma and the thousands separator is the stop.

[New Judge]

I should also add that this answer provides the weight in tonnes (i.e. the metric measure which is equal to 1,000 kg).

145 tonnes is equivalent to approximately 142.5 long tons (the UK version, 2,240 pounds) or 159.6 short tons (the US version, 2,000 pounds).

[mibn2cweus]

This might help you to remember the area of a circle -

"Pi R^2"

"No, pie are round . . . cornbread are squared."

. . . or maybe not.