Question

the internal and external radius of a metallic cylinder are 3 cm and 3.5 CM respectively if the length of the pipe is 56 cm find its total surface area use Pi 3.14

Answer 1

Answer: $1230.88$ $cm^2$

Step-by-step explanation:    

Since, the total surface area of the pipe

= curved surface area of external cylinder + 2 × area of circle of radius 3.5 - 2 × area of circle of radius 3

= $2\pi (3.5)56+ 2\pi(3.5)^2-2\pi(3)^2$

= $2\pi [3.5\times 56+ 12.25-9]$

= $2\pi [196+ 12.25-9]$

=  $2\times 3.14 \times 199.25$

=  $1230.88$

Thus, the required area = 1230 square cm.

Answer 2

Total surface area of cylinder having internal and external radius 3 cm and 3.5 CM respectively and length of the pipe is 56 cm is given by the formula= 2 π (R -r)H+2π(R²-r²)

= π×[ 2 ×(3.5 -3)×56+2×(3.5²-3²)]

= π×[56+2×(12.25-9)]

= 3.14 × [56 + 6.50]

=3.14 × 62.50

=196.25 cm²