The rate of simple interest for the first 3 years is 6%, 7% for the next 4 years and 7.5% for further 7 years. Mohan invested Rs.18800 for 11 years. Find the simple interest?

For simple interest with varying rates, calculate interest for each time period separately and sum them. Years 1-3 at 6%: (18800×6×3)/100 = 3384. Years 4-7 at 7%: (18800×7×4)/100 = 5264. Years 8-11 at 7.5%: (18800×7.5×4)/100 = 5640. Note that only 4 years apply at 7.5% (not 7), since total period is 11 years. Total interest = 3384 + 5264 + 5640 = 14288.