Question

Need the ans ....It is ssoo urgent...
A metallic right circular cylinder is 15 cm high and diameter of its base is 14 cm.It is melted and recasted into another cylinder with radius 4 cm.Find the height ,CSA and TSA.

Answer 1

first metallic cylindr:- volume =πr²h
=π*7*7*15
=735π.
It is recasted, right!
Then, the volume is πr²h, but the radius and the height are different. The radius =4cm, right!
Then, volume =π*4*4*h
=16πh.
735π=16πh
735=16h
h= 45.9375cm, right!
C.S.A. = 2πrh = 2*π*4*45.9375
= 1155cm²
T.S.A. = C.S.A. + 2πr²
=1155+32π
=1155+100.57
1255.57cm² ( for the recasted cylinder).
Hope this will help you.

Answer 2

r of 1st cylinder=7 cm
height=15 cm
volume=πr²h=π*49*15=2309.07 cm³

r of second cylinder=4 cm
volume has no change it is 2309.07 cm³
2309.07=π*16*H=50.26 H
H=2309.07/50.26
height of the second cylinder=45.94 cm

tsa=2πr(r+h)
=2*π*4(4+45.94)=1255.12 cm²

csa=2πrh
=2*π*4*45.94
=1154.59 cm²