Rajiv has a recurring deposit account in a bank of ₹ 600 per month. If the bank pays the interest at 7% p.a. and he gets ₹ 15450 as maturity amount, the total time period is ______.

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Rajiv has a recurring deposit account in a bank of ₹ 600 per month. If the bank pays the interest at 7% p.a. and he gets ₹ 15450 as maturity amount, the total time period is 24 months. Explanation: Given: Monthly deposit, P = ₹ 600 Rate of interest, r = 7% p.a. Maturity value, MV = ₹ 15450 MV = (Pxxn(n+1)xxr)/(2xx12xx100) `15450 = 600n + (600xxn(n+1)xx7)/(2400) 15450 = 600n+ (4200n(n+1))/2400 => 15450 = 600n + (7n(n+1))/4` 61800 = 2400n + 7n(n + 1) $\Rightarrow$ 61800 = 2400n + 7n2 + 7n $\Rightarrow$ 7n2 + 2407n − 61800 = 0 Solve the quadratic equation: n2 + 343.86n − 8828.57 = 0 Total deposit = 600 ⋅ 18 = ₹ 10800 Interest = (600xx18xx19xx7)/2400 =$\frac{1436400}{2400}$ = ₹ 598.5 MV = ₹ 10800 + ₹ 598.5 = ₹ 11398.5 Try n = 24: Deposit = ₹ 14400 Interest = (600xx24xx25xx7)/2400 = $\frac{2520000}{2400}$ = ₹ 1050 MV = ₹ 15450 24 months = 2 years

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