Q. A sum of money at some rate of simple interest amounts to 2900 Rs. in 8 years and to 3000 Rs. in 10 years. The rate of interest per annum is :
Answer: 2%
Notes: Principal + interest for 8 years = 2900 Rs…………(I) Principal + interest for 10 years = 3000 Rs……..…(II) Subtracting equation (I) from (II) Interest for 2 years = 100 Rs. ∴ Interest for 8 years = 400 Rs. From equation (I), Principal = (2900 - 400) = 2500 Rs. $latex \therefore Rate = \frac{SI\times 100}{Princ.\times Time}&s=1$ $latex = \frac{400\times 100}{8\times 2500} = 2\%&s=1$ Hence option [A] is correct answer.

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