1. **State the problem:** Find the sum of $3 \times 10^6$ and $3 \times 10^6$. 2. **Recall the formula:** When adding numbers in scientific notation with the same power of 10, add the coefficients and keep the power of 10 the same. 3. **Apply the rule:** $$3 \times 10^6 + 3 \times 10^6 = (3 + 3) \times 10^6$$ 4. **Simplify the sum:** $$= 6 \times 10^6$$ 5. **Interpretation:** The sum is $6$ million. **Final answer:** $6 \times 10^6$