Question

The thickness of the material of a
hollow cylinder is 4cm and its
outer diameter is 20cm. If height of
cylinder is 35cm, then the total
surface area is​

Answer 1

Step-by-step explanation:

Correct option is

A

3168

We have,

Height of pipe (h)=20 cm

External diameter =25 cm

External radius (R)=25/2=12.5 cm

Internal diameter =25−(1+1)=23 cm

Internal radius (r)=23/2=11.5 cm

Total surface area

=2π(R+r)(R−r+h)

=2π(12.5+11.5)(12.5−11.5+20)

=2π(24)(21)

=1008π cm

2

=3168 cm

2

Hence, the total surface area of the cylinder =3168 cm

2

.

Answer 2

Here,

D= 20cm

R= 10cm

r= 10-4= 6cm

h=35cm

we know that total surface area of a hollow cylinder

= 2π(R+r)(R-r+h)

=2π(10cm+6cm)(10cm-6+35cm)

= 2×22×16cm×39cm/7

=44×16cm×39cm/7

=44× 624cm²/7

=27456cm²/7

= 3922.28cm²