Question

I'll mark you brianlist if you give first answer​

Answer 1

Answer:

Step-by-step explanation:

R= external radius =  2 /25  = 12.5 cm.

r= internal radius = ( external radius − thickness ) =(12.5−1)=11.5 cm .

h = length of the pipe =20 cm .

∴ total surface area of the pipe  = (external curved surface ) + (internal curved surface ) +2 (area of the base of the ring ).

=2πRh+2πrh+2(πR ^ 2  −πr  ^2  )

=2π(R+r)h+2π(R  ^2 −r  ^2  )

=2π(R+r)(h+R−r)

=2×  22/7  × (12.5+11.5) × (20+12.5−11.5)cm^ 2

=2×  22/7  × 24 × 21 cm^ 2

 = 3168 cm ^2

Answer 2

Answer:

2058π $cm^{2}$

Step-by-step explanation:

exterior diameter is 25 cm

So, the surface arc outside the arc will be (25π × 21) $cm^{2}$

Pipe is one cm thick, so the interior diameter will be (25 - 2) =23 cm

So, the surface arc inside the arc will be (23π × 21) $cm^{2}$

So, the total surface arc outside the arc will be

(25π × 21) +(23π × 21)  $cm^{2}$  = 98π × 21 $cm^{2}$ =2058π $cm^{2}$