CBSE Class 9 Answered

The wire has weight 13.2 Kg=13200 gm

Now from the weight we can find the volume of the wire as   it's given that when copper weighs 8.4 gm its vol is 1 cu.cm.

 So when copper weighs 13200 gm, its volume =(13200/8.4) cu.cm= ( 11000/7) cu.cm

Now, let the length of the copper wire be l cm

We know that the shape wire is like the shape of a right circular cylinder.Let the radius of the wire =r.

So according to question , r=diameter/2=2 mm =2/10 cm

So volume of the wire ==(22/7)*(2/10)*(2/10)*(l).

Thus ,

 we have the equation,

(22/7)*(2/10)*(2/10)*(l)= (11000/7)

Solving we get

l=12500 cm