A certain sum invested on compound interest at 10% per annum compounded annually amounts to ₹19404 in 18 months. What was the sum invested (in ₹) ?

16800

Amount = Principal × ( 1 + \(\frac{r}{100}\))ⁿ

So, Amount after 18 months = Principal + CI

= 100 + 10 + 5.5

= 115.5

According to question, 115.5R = 19404

1R = 168

So, 100R = 16800

Principal is = 16800

The correct answer is option (4) : 16800