1.  A sum invested at 5% simple interest per annum grows to ₹ 504 in 4 years. The same amount at 10% simple interest per annum in 2 years will grow to :
A. ₹ 420
B. ₹ 450
C. ₹ 525
D. ₹ 550

Answer: Option C

Explanation:

Let the sum be ₹ X. Then,

S.I. = ₹ (504 - X).

∴ X x 5 x 4 = 504 - X
100

<=> 20X = 50400 - 100X

<=> 120X = 50400

<=> X = 420.

S.I. = ₹ 420 x 10 x 5 = ₹ 105.
100 x 2

Now, P = ₹ 420, R = 10%, T = 5/2 years.

Amount = ₹ (420 + 105) = ₹ 525.