Given:
- A sum becomes ₹20,070 after 3 years
- The same sum becomes ₹30,105 after 6 years
- Compound interest is applied
The time difference between the two amounts is exactly 3 years.
The amount at year 6 is the amount at year 3 grown for another 3 years.
Growth factor for 3 years =Amount at 3 yearsAmount at 6 years
Growth factor =20,07030,105
Growth factor =1.5
The money grew 1.5 times in 3 years.
The principal also grows by a factor of 1.5 in 3 years to reach ₹20,070.
Principal ×1.5=20,070
Principal =1.520,070
Principal =13,380
Therefore, the original sum is ₹13,380.