A person invested a sum of ₹10,500 at x% per annum at simple interest and a sum of ₹13,500 at (x + 2)% p.a. at simple interest. If the total interest earned on both the investments for 3 years is ₹7,650, then the rate of interest on the first investment is:

9.5%

By using formula ,

Simple Interest = \(\frac{Principal ×Rate × Time }{100}\)

ATQ,

\(\frac{10500 × x × 3 }{100}\)  +  \(\frac{13500 ×(x+2)× 2 }{100}\) = 7650

(105 × x × 3)  +  (135 ×(x+2)× 3 ) = 7650

315x + 405x + 810 = 7650

720x = 6840

x = 9.5%