Face Value of a share = Rs.60

He bought each share at Rs.60 - Rs.5 = Rs.55

Number of shares = 40

Dividend = 12$\dfrac{1}{2}$% = $\dfrac{25}{2}$%

Dividend per share = $\dfrac{60 \times 25}{2 \times 100} $= Rs. 7.5%

Total dividend = $(40 \times 7.5)$

ie, He got a dividend of $(40 \times 7.5)$ for an investment of Rs.$(40 \times 55)$

Interest obtained = $\dfrac{40 \times 7.5 \times 100}{40 \times 55}$ = 13.64%