To add $7 \times 10^{-6}$ and $2.1 \times 10^{-5}$, follow these steps:

Step 1: Convert to the same power of 10

We can convert $7 \times 10^{-6}$ to a power of $10^{-5}$.

Since $7 \times 10^{-6}$ is the same as $0.7 \times 10^{-5}$, the addition becomes: $0.7 \times 10^{-5} + 2.1 \times 10^{-5}$

Step 2: Add the coefficients

Now, add the coefficients: $0.7 + 2.1 = 2.8$

Step 3: Combine the result with the power of 10

Thus, the result is: $2.8 \times 10^{-5}$

So, $7 \times 10^{-6} + 2.1 \times 10^{-5} = 2.8 \times 10^{-5}$.

Would you like more details or have any questions?

Here are five related questions:

1. How do you subtract numbers in scientific notation with different exponents?
2. What are some applications of scientific notation in real life?
3. How do you multiply numbers in scientific notation?
4. How do you divide numbers in scientific notation?
5. What is the process for converting scientific notation back to standard form?

Tip: Always make sure to align the exponents when adding or subtracting in scientific notation. This simplifies the calculation and ensures accuracy.