For simple interest: SI = P×R×T/100. Given: Principal = Rs. 4800, Amount = Rs. 6480, Time = 7 years. Interest earned = 6480 - 4800 = Rs. 1680. Using the formula: 1680 = 4800×R×7/100. Solving: R = (1680×100)/(4800×7) = 168000/33600 = 5%. Therefore, the rate of simple interest is 5% per annum.