We use the formula for Simple Interest:
\[ \text{Simple Interest} = \frac{P \times R \times T}{100} \]
Veeru's yearly interest: \[ = \frac{10000 \times 5 \times 1}{100} = ₹500 \]
Joy's yearly interest: \[ = \frac{8000 \times 10 \times 1}{100} = ₹800 \]
\[ \text{Time} = \frac{₹3000}{₹300 \text{ per year}} = 10 \text{ years} \]
Veeru has already invested for 2 years. To match Joy’s total, he must invest for:
\[ 2 + 10 = \boxed{12 \text{ years}} \]
For any natural number $k$, let $a_k = 3^k$. The smallest natural number $m$ for which \[ (a_1)^1 \times (a_2)^2 \times \dots \times (a_{20})^{20} \;<\; a_{21} \times a_{22} \times \dots \times a_{20+m} \] is: