Aptitude - Volume and Surface Area - Discussion

4. 

66 cubic centimetres of silver is drawn into a wire 1 mm in diameter. The length of the wire in metres will be:

[A]. 84
[B]. 90
[C]. 168
[D]. 336

Answer: Option A

Explanation:

Let the length of the wire be h.

Radius = 1 mm = 1 cm. Then,
2 20

22 x 1 x 1 x h = 66.
7 20 20

h = 66 x 20 x 20 x 7 = 8400 cm = 84 m.
22


Anju said: (Sep 16, 2010)  
From where d 22/7 came?

Richa said: (Dec 2, 2010)  
Its formula pai*r^2*h.

Pai's value is 22/7.

I'm not gettng the sign of pai in computer. Ok.

Rakesh said: (May 28, 2011)  
When 1mm diameter is converted into radius it is .5 mm or .5/1000 meter.

Prasad said: (Aug 6, 2011)  
Simple. The volume is given in mm and the length in meters. Hence the length should be minimal.

Rashmi said: (Jan 10, 2012)  
Can anybody say me how did we get 1/20?

Deepi said: (May 2, 2012)  
@ Rashmi,
1cm=10milimeter
to convert mm into cm we have to multiply it by 10

Ayush said: (May 22, 2012)  
Please tell why the shape of wire is considered as cylinder?

Mystery said: (Oct 10, 2012)  
@Ayush.

Because the wire is so small people don't tend to think of it as a cylinder but it is.

It is long and has very small radius!

Hi Everybody said: (Jan 14, 2013)  
Actaully wire is of the form:: CYCLINDER

we know,
volume of cyclinder = π*r^2* h----------- (1)

r-radius
h-height(lenth)
Given
Diameter(d)=1mm
so r=d/2
r=(1/2)mm
r=(1/20)cm

Substitute in Eqn (1)

22/7 * (1/20)^2 *h =66 (given)

h =66 x 20 x 20 x 7/22
= 8400 cm = 84 m.

Gautam Singh said: (Feb 5, 2015)  
1cm = 10 millimeter.

To convert km into cm we have to multiply it by 10.

Megha said: (Mar 26, 2015)  
Still I didn't get how we get 1/20? Please explain me step by step.

Rohini said: (Jun 10, 2015)  
They have given d diameter. But we need radius. So when 1 mm is divided by 2, we get 1/2 mm and to convert mm into cm we have to multiply it by 10.

Therefore, 1/2 multiply by 10, we get 1/20.

Uma said: (Oct 7, 2015)  
How we know that the wire convert into cylinder form, may be its convert other shapes.

Adil said: (Jan 1, 2016)  
Please tell the formula.

Archana said: (May 27, 2016)  
@Adil.

Formula of volume of cylinder is Pi * r * r * h.

Avani said: (Jun 12, 2016)  
@Rashmi, @Megha.

1cm=10mm.
? =1/2mm.
Cross multiplication

1/2 * 1/10.
= 1/2 * 10.
= 1/20 m.

Aboo Farhan said: (Aug 13, 2016)  
We know that d = 2r then r = d/2mm and here d is given 1mm and 1mm convert in cm then r = 1/20cm.

Amit said: (Aug 14, 2016)  
1/2 * 10 = 5 >_<.

But.

1/2 = .5 mm.

And to convert it into cm we have to divide it by 10.

So, .5/10 = .05cm.

5/100 = 1/20 cm.

Amit said: (Aug 14, 2016)  
1/2 is divided by 10.

1/2/10 = 1/2/10 (1/2/10/1 same thing).

Then.

1/2 * 1/10 = 1/20.

Suhani Bajpai said: (Sep 10, 2016)  
What is meant by 66 cubics? and why is it equal to the volume of a cylinder?

Ashok said: (Sep 16, 2016)  
@Suhani.

Yes. I too have same doubt.

Can anyone explain us please?

Sateesh Kumar Routhu said: (Sep 30, 2016)  
1 cubic centimeter equal to 1 millilitre volume of liquid, in this question silver metal liquid is used to make a wire, the wire is in the shape of cylinder , so we have to form silver wire, then 66 cubic centimeter silver metal liquid is changed to volume of the wire (Wire is in the form of cylinder, assume long thin wire. The length of the wire is also the height of the cylinder) then by using formula of the volume of the cylinder we can find the length of the wire, the formula is:
V = πr^2h.
Radius = diameter/2 = 1/2 mm
i.e To convert mm to cm use the following formula:
1 mm = 0.1 cm.
So, to convert 0.5 mm to cm, multiply 0.1 by 0.5.
i.e. 0.5 mm = 0.1 * 0.5 cm = 0.05 cm or 1/20 cm.
Then according to formula,
66 cubic cm silver metal liquid is equal to the volume of the wire.
Then, 22/7 * 1/20 * 1/20 * h = 66.

h = 66 * 20 * 20 * 7/22,
= 8400 cm,
= 84 m.

Mr. Mp said: (Aug 26, 2017)  
1/2 mm is (1/2)*10^-3 or (1/2)* 1/1000 or (1/20)* (1/100) or (1/20)*10^-2 .

10^-2 metre is nothing but centimetre

Shiwani said: (Sep 17, 2017)  
1mm=1/1000m, so 1/2000m.

And 1m=100cm, so 1/2000m=1/20cm.

Annu said: (Sep 20, 2017)  
I can't understand this.

Chenga said: (Jan 20, 2018)  
Please tell why the shape of wire is consider as a cylinder?

Jai said: (Mar 3, 2019)  
Because the wire is in the shape of a cylinder.

Prashanth said: (Jul 19, 2019)  
1cm = 10mm.

Post your comments here:

Name *:

Email   : (optional)

» Your comments will be displayed only after manual approval.