8 months = \(\cfrac{8}{12}\) years
Since the annual interest is \(\cfrac{1}{16}\) of the principal:
Interest for 1 year on ₹690 = \( 690 \times \cfrac{1}{16} \)
\(\therefore\) Interest for 8 months on ₹690:
\( = \cancel{690}115 \times \cfrac{1}{\cancel{16}2} \times \cfrac{\cancel8}{\cancel{12}2} \)
\( = \cfrac{115}{4} \)
\( = 28.75 \)
Let me know if you need any refinements!