A circular pipe has an external diameter of 42 cm and an internal diameter of 36 cm. Find the area of the cross-section of the pipe.
Show answer & explanation
Correct answer: A
Explanation
Given:
Outer diameter = 42 cm
Inner diameter = 36 cm
By formula:
Area of circle = πr²
Area of pipe = π(R² − r²)
Outer radius R = 42 / 2 = 21 cm
Inner radius r = 36 / 2 = 18 cm
Area = π(21² − 18²)
= π(441 − 324)
= π × 117
= 22/7 × 117
= 367.57 cm² (approximately)