A ring-shaped disc has outer radius 10 cm and inner radius 7 cm. What is the…
2025
A ring-shaped disc has outer radius 10 cm and inner radius 7 cm. What is the approximate ratio of the ring's area to the whole outer circle?
- A.
1:2
- B.
2:3
- C.
3:4
- D.
4:5
Show answer & explanation
Correct answer: A
1. Outer circle area = π(10)² = 100π. 2. Inner circle area = π(7)² = 49π. 3. Ring area = 100π - 49π = 51π. 4. Ratio of ring area to outer circle = 51π : 100π = 51:100.