The diameter of roller 1.5 m long is 84 cm.

Solution:

Given that

Diameter of the roller (d) = 85 cm = 0.84 m

Length of the roller = 1.5 m

Radius of the roller(r) = d/2

= 0.842 = 0.42 m

The total area of the playground covered by the roller in one revolution=covered area of the roller

Curved surface area of the roller = 2πrh

= 2 * 3.14 * 0.42 * 1.5

$=0.12 * 22 * 1.5 \mathrm{~m}^{2}$

Area of the playground = 100 * Area covered by roller in one revolution

$=(100 * 0.12 * 22 * 1.5) \mathrm{m}^{2}$

$=396 \mathrm{~m}^{2}$

Now,

Cost of leveling $1 \mathrm{~m}^{2}=50 \mathrm{p}=$ Rs $0.5$

Cost of leveling $396 \mathrm{~m}^{2}=$ Rs. $396 * 0.5=$ Rs. 198

Hence, cost of leveling $396 \mathrm{~m}^{2}$ is Rs. 198