Explanation:

- Find the original sum. If something increases by 15% to become Rs19,320, you calculate the original sum by dividing Rs19,320 by 1.15.

- Calculating the original sum:

- Rs19,320 / 1.15 = Rs16,800

- Verify with the options:

- Option 1: Rs16,800 ()

- 15% of Rs16,800 is Rs2,520. Adding Rs2,520 to Rs16,800 gives Rs19,320.

- Option 2: Rs16,000

- 15% of Rs16,000 is Rs2,400. Adding Rs2,400 to Rs16,000 gives Rs18,400.

- Option 3: Rs17,000

- 15% of Rs17,000 is Rs2,550. Adding Rs2,550 to Rs17,000 gives Rs19,550.

- Option 4: Rs17,800

- 15% of Rs17,800 is Rs2,670. Adding Rs2,670 to Rs17,800 gives Rs20,470.

- Conclusion: The original sum is Rs16,800.