2020 · Q88
Four circular coins of equal radius are placed with their centres coinciding with four vertices of a square. Each coin touches two other coins. If the uncovered area of the square is 42 cm², then what is the radius of each coin? (Assume π = 22/7)
Elementary MathematicsCircles
- A5 cm
- B7 cm
- C10 cm
- D14 cm
Explanation
Uncovered area = r^2(4-pi) = 42 with pi = 22/7 gives r^2*(6/7) = 42, so r = 7 cm. Hence option (B). Check: 49*(4-22/7) = 49*6/7 = 42, the given uncovered area.