Rs. 8000 invested at compound interest gives Rs. 1261 as interest after 3 years. The rate of interest per annum ? रू. 8000 पर तीन वर्षों का ब्याज चक्रवृद्धि ब्याज दर से रू. 1261 है। ब्याज दर ज्ञात कीजिए।

Using compound interest formula: A = P(1 + r/100)³. Interest = 8000[(1 + r/100)³ - 1] = 1261. Therefore (1 + r/100)³ = 9261/8000 = 3.5³/4³ = (3.5/4)³. Taking cube root: 1 + r/100 = 3.5/4 = 0.875. Thus r/100 = -0.125, giving r = 5%. Option A (25%) would give much higher interest of Rs. 1953. Option B (17.5%) would give Rs. 4629. Option C (10%) would give Rs. 2648.