Q. A sum of money lent out at simple interest amounts to 720 Rs. after 2 years and to 1020 Rs. after a further period of 5 years. The sum is :
Answer: 600 Rs.
Notes: Principal + SI for 2 years = 720 Rs. ……(I) Principal + SI for 7 years = 1020 Rs. ……(II) Subtracting equation (I) from (II), S.I. for 5 years = (1020 - 720) = 300 Rs. ∴ S.I. for 2 years $latex = 300\times \frac{2}{5} = 120 Rs.&s=1$ ∴ Principal = (720 - 120) = 600 Rs. Hence option [B] is correct answer.

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