DRDO Multi tasking staff Model paper 4

We know that,
Compound interest = P [(1 + r/100)‌n – 1]
Where,
P = principal amount
r = rate of interest
n = no. of years
⇒ 2100 = p [(1 + 10/100)‌2– 1]
⇒ p = 2100/(21/100) = Rs. 10,000