If 5 men working 8 hours a day earn Rs. 5,000 in 15 days. Then how much will 15 men working 6 hours a day earn (in Rs.) in 15 days?

Given 5 men working 8 hours a day earn Rs. 5,000 in 15 days

it implies that $5\times 8\times 15=600$ man hours can earn 5000 rupees. 

Hence, one man hour cost is $\frac{5000}{600}=\frac{25}{3}$ Rupees

The number of man hous when 15 men working 6 hours in 15 days, is $15\times 6\times 15=1350$

Hence the earning is $\left(1350\right)\times \frac{25}{3}=450\times 25=\boxed{\mathbf{R}\mathbf{s}\mathbf{ }\mathbf{11}\mathbf{,}\mathbf{250}}$