Q.If an amount becomes 520 rupees in 5 years and 568 rupees in 7 years, then the principal amount is— (a) ₹ 400 (b) ₹ 500 (c) ₹ 600 (d) ₹ 700
Answer: A
(7-5) years or 2 years' interest amount = (568-520) rupees = 48 rupees
\(\therefore \) 1 year's interest amount = \(\cfrac{48}{2}=24\) rupees
\(\therefore\) 5 years' interest amount = 24\(\times\)5 rupees

= 120 rupees

\(\therefore\) Principal amount = (520-120) rupees

= 400 rupees

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