The diameter of a roller, 1 m long, is 84 cm. If it takes 500 complete revolutions to level a playground,
Question:
The diameter of a roller, 1 m long, is 84 cm. If it takes 500 complete revolutions to level a playground, the area of the playground is
(a) 1440 m2
(b) 1320 m2
(c) 1260 m2
(d) 1550 m2
Solution:
(b) 1320 m2
Area covered by the roller in 1 revolution $=2 \pi r h$
$=2 \times \frac{22}{7} \times 42 \times 100$
$=44 \times 600$
$=26400 \mathrm{~cm}^{2}$
$\therefore$ Area covered in 50 revolutions $=26400 \times 500 \mathrm{~cm}^{2}$
$=1320 \mathrm{~m}^{2}$
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