A sum of money at simple interest amount to Rs 6,000 in 4 year and to Rs 6750 in 7 years at same rate of interest find the sum ? साधारण ब्याज पर एक राशि 4 साल में 6,000 रुपये और समान ब्याज दर पर 7 साल में 6750 रुपये हो जाती है, तो राशि ज्ञात कीजिए?

The interest for 3 years (difference between 7 and 4 years) is Rs 750 (6750 - 6000). So annual interest is Rs 250. Interest for 4 years would be Rs 1000, therefore the principal sum is Rs 5000 (6000 - 1000). We can verify: 5000 at 5% simple interest for 4 years gives 5000 + 1000 = 6000, and for 7 years gives 5000 + 1750 = 6750.