Sanjana invested Rs. 15000 in SI at the rate of 2x% per annum for two years and the same amount is invested in CI at the same rate of interest if she received Rs.150 more interest than S.I, then find the rate of interest per annum? A. 15% B. 10% C. 20% D. 19% Answer Workspace Report Discuss Answer with explanation Answer: Option B Explanation CI – SI = 150 P(1 + r/100)n – Pnr/100 = 150 15000[(1 + (2x/100))2 – 1] – (15000*2x*2)/100 = 150 15000[((100 + 2x)/100)2 – 1] – 600x = 150 15000[(10000 + 400x + 4x2)/10000 – 1] – 600x = 150 15000[(10000 + 400x + 4x2 – 10000)/10000] – 600x = 150 15000[(400x + 4x2)/10000] – 600x = 150 3/2(400x + 4x2) – 600x = 150 (3*4/2)(100x + x2) – 600x = 150 600x + 6x2 – 600x = 150 6x2 = 150 x2 = 25 x = 5 The rate of interest per annum = 2x% = (2*5)% = 10% Workspace
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