A sum of money amounts to 850 Rs. in 3 years and to 925 Rs. in 4 years at some rate of simple interest. The sum is :

A sum of money amounts to 850 Rs. in 3 years and to 925 Rs. in 4 years at some rate of simple interest. The sum is :
[A]550 Rs.
[B]600 Rs.
[C]625 Rs.
[D]700 Rs.

625 Rs.
Interest for 1 year= (925 – 850) = 75 Rs.
∴ If a sum becomes a_{1} in t_{1} years and a_{2} in t_{2} years then rate of interest
= \frac{100(a_{2}-a_{1})}{a_{1}t_{2} - a_{1}t_{1}}\%
= \frac{100(925-850)}{850\times 4- 3\times 925} = \frac{7500}{625} = 12\%
\therefore Principal = \frac{SI\times 100}{Time\times Rate}
= \frac{75\times 100}{1\times 12} = 625\ Rs.
Hence option [C] is correct answer.

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