Find simple interest on Rs.600 for 3 years at 5% per annum. Also find the amount.
$
  {\text{A}}{\text{. Rs }}680 \\
  {\text{B}}{\text{. Rs 685}} \\
  {\text{C}}{\text{. Rs 690}} \\
  {\text{D}}{\text{. Rs 695}} \\
 $

Hint: Here we go through by the formula of simple interest that we study in the chapter of simple interest i.e. $SI = \dfrac{{P \times R \times T}}{{100}}$. By this formula we will be able to calculate the simple interest.

Complete step-by-step answer:
Here in the question the principal amount is a given as Rs.600
I.e. P= Rs.600
Here the give time T=3 years
And the given rate is R=5%.
And we know that the formula of calculating the simple interest is $SI = \dfrac{{P \times R \times T}}{{100}}$.
So now we put the given values in the formula to find out the simple interest.
$
   \Rightarrow SI = \dfrac{{600 \times 5 \times 3}}{{100}} \\
   \Rightarrow SI = 90 \\
  \therefore SI = 90 \\
 $
And as we know that for calculating the amount we will add the simple interest to the principal amount.
I.e. Amount= SI + P=90+600=690
Therefore the required amount is Rs.690.
Hence option C is the correct answer.

Note: - Whenever we face such a type of question, the key concept for solving the question is to first write the given terms so as not to be confused. And simply put these terms in the formula and calculate the terms that we have to find.