2016 · Q58
Four equal discs are placed such that each one touches two others. If the area of empty space enclosed by them is 150/847 square centimetre, then the radius of each disc is equal to
Elementary MathematicsMensuration
- A7/6 cm
- B5/6 cm
- C1/2 cm
- D5/11 cm
Explanation
The four centres form a square of side 2r. The enclosed empty area is 4r²−πr² = r²(4−π). With π = 22/7: r²·(6/7) = 150/847, so r² = 25/121. Hence r = 5/11 cm, option D.