S.I for `1 1/2 `Years `= Rs. (1067.20 - 1012)` `= 55.20` S.I for `2 1/2` years `= Rs. (55.20 xx 2/3 xx 5/2)` `= Rs.92` `:. principal = Rs. (1012 - 92)` `= Rs. 920` `:. Rate = (100 xx 92 xx 2)/(920 xx 5)` `= 4%`