2020 · Q76
A bicycle wheel makes 5000 revolutions in moving 11 km. What is the radius of the wheel? (Assume π = 22/7)
Elementary MathematicsCircles
- A17.5 cm
- B35 cm
- C70 cm
- D140 cm
Explanation
Circumference = 11000/5000 = 2.2 m, so r = 2.2/(2*pi) = 0.35 m = 35 cm (pi = 22/7). Hence option (B). Check: 2*pi*35 cm ~= 220 cm = 2.2 m per revolution, and 5000*2.2 m = 11 km.