What will be the ratio of simple interest earned by a certain amount at the same rate of interest for 6 years and 9 years?

 Ratio of simple interest earned by a certain amount at the same rate of interest for 6 years and 9 years is

$$\frac{P1 \times R1 \times t1}{100} : \frac{P2 \times R2 \times t2}{100}$$

Where, P1 and P2 = P ; R1 and R2 = R (as the principle and rate of interest for both the cases are same)

t1 = 6 ; t2 = 9

$$\frac{P \times R \times 6}{100} : \frac{P \times R \times 9}{100}$$

$$ 6 : 9 $$ (or) $$ 2 : 3$$

Hence, option C is the correct answer.