After two successive yearly cuts of 10% each, a solar lamp in a Bhubaneswar store now costs ₹4860. What did it cost two years ago?

Two 10% cuts multiply to $0.90\times 0.90=0.81$, so $0.81\times P=4860$ → $P=\frac{4860}{0.81}=6000$. Check: 6000 → 5400 → 4860. Trap: treating the two cuts as one 20% gives ₹6075, adding 20% back onto ₹4860 gives ₹5832, and ₹5346 undoes only one of the two years.