A worker is paid Rs 210 for 6 days work.

Let x be the number of days for which the worker is paid Rs 875.

Since the income of the worker and the number of working days are in direct variation, we have:

$\frac{210}{875}=\frac{6}{x}$

$\Rightarrow 210 \times x=875 \times 6$

$\Rightarrow x=\frac{875 \times 6}{210}$

$=\frac{5250}{210}$

$=25$

Thus, the required number of days is 25 .