What rate per cent does Shantanu get for his money in discounting a bill due 30 months hence he deducts 30% of the amount of the bill?

Let the amount of the bill = ₹ 100.
Money deducted = ₹ 30
Money received by the holder of the bill = ₹ (100 - 30) = ₹ 70
SI on ₹ 70 for 30 months = ₹ 30
∴ Rate = [100 x 30] / [70 x (30/12)]% per annum
= (10 x 3 x 12) / 21 %
= (10 x 12) / 7 %
= 120/7 %
= 17¹/₇ %