If the interest of Tk. M at M% in 4 years is Tk. M, then M = ?

A 20

B 25

C 30

D 32

Correct Answer: Option B

Here,
P = M
r = M%
I = M
n = 4

We know that,
I = Pnr
M = M × 4 × (M/100)
⇒ 1 = M/25
∴ M = 25