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# maths question

ok so you have a hot water cylinder with a radius of 20cm and a height of 120cm, what is the volume of the cylinder in cubic centimetres using the formulas pi R2h
and pi being 3 not the 3.14.
????

Reckon it is 144,000 cm3

pi is neither 3 not 3.14 but, if you must...

Volume of a cylinder is the area times the height. Area is pi times the square of the radius.

So volume = 3 x (20 x 20) x 120 = 3 x 400 x 120 = 144,000cm^3

3(pi)x (20x20) r squared) x 120 (height)

3x400x120

144,000 cm3 (cubed)

Why ask us when you have all the information and the actual formula? oO

Original Poster

pi is 3.142 or to be pricise 3.14159265 so when i said 3.142 that was pi rounded to 3 decimal places.

ro53ben

pi is neither 3 not 3.14 but, if you must...Volume of a cylinder is the … pi is neither 3 not 3.14 but, if you must...Volume of a cylinder is the area times the height. Area is pi times the square of the radius.So volume = 3 x (20 x 20) x 120 = 3 x 400 x 120 = 144,000cm^3

Edited by: "shamus1975" 15th Nov 2010

Original Poster

and your all correct so part 2 easy part

one cubic centimetre of water weighs 0.001kg. so when the cylinder is full what will the water weigh in KG's.

cdm22

Why ask us when you have all the information and the actual formula? oO

^^^^^This^^^^^

shamus1975

and your all correct so part 2 easy partone cubic centimetre of water … and your all correct so part 2 easy partone cubic centimetre of water weighs 0.001kg. so when the cylinder is full what will the water weigh in KG's.

Can you seriously not work this out yourself???

shamus1975

and your all correct so part 2 easy partone cubic centimetre of water … and your all correct so part 2 easy partone cubic centimetre of water weighs 0.001kg. so when the cylinder is full what will the water weigh in KG's.

Depends. 1ml of water only weighs one gramme at 4 degrees Celcius. This is a hot water tank, so the water will have expanded and have a lower overall density.

So we need to know the temperature of the water in the tank and also whether the volume of the tank is measured when cold or hot.

144kg at STP

cannyscot

144kg at STP

Actually, no. STP is either 0C or 20C and the water wouldn't weigh 144kg at either of those.

In fact, there are many definitions of STP but none of them involve 4 Celcius.
Edited by: "ro53ben" 15th Nov 2010

ro53ben

Actually, no. STP is either 0C or 20C and the water wouldn't weigh 144kg … Actually, no. STP is either 0C or 20C and the water wouldn't weigh 144kg at either of those.In fact, there are many definitions of STP but none of them involve 4 Celcius.

Quite so, but since you and the original poster are using mass and weight as synonymous and the OP is taking Pi as 3, 144 is a good enough approximation.
Edited by: "cannyscot" 15th Nov 2010

cannyscot

Quite so, but since you and the original poster are using mass and weight … Quite so, but since you and the original poster are using mass and weight as synonymous and the OP is taking Pi as 3, 144 is a good enough approximation.

Agreed

Original Poster

yes cant you its just a bit of afternoon trivia i noticed you never answered

civms47

Can you seriously not work this out yourself???

Edited by: "shamus1975" 15th Nov 2010

Original Poster

yeah just a question we set in a quiz, did not think of the temperture coming into effect, lets hope we dont get some clever person answering lol.
well done any ways.

ro53ben

Agreed

Who on god's earth would approximate pi to 3? 150kg is much closer to the answer (and simpler) than 144kg.

Original Poster

its simplified for a pub quiz, its a bit of fun not a real life renovation product

jah128

Who on god's earth would approximate pi to 3? 150kg is much closer to the … Who on god's earth would approximate pi to 3? 150kg is much closer to the answer (and simpler) than 144kg.