Answer :

To solve the mathematical expression [tex]\(2.1 \times 10^3 \times 1.2 \times 10^2 + 1.5 \times 10^{01}\)[/tex], let's break it down step by step.

1. Identify the terms in the expression:

- The first term is [tex]\(2.1 \times 10^3\)[/tex].
- The second term is [tex]\(1.2 \times 10^2\)[/tex].
- The third term is [tex]\(1.5 \times 10^1\)[/tex].

2. Evaluate the first term:

[tex]\(2.1 \times 10^3 = 2100.0\)[/tex]

3. Evaluate the second term:

[tex]\(1.2 \times 10^2 = 120.0\)[/tex]

4. Multiply the results of the first two terms:

[tex]\[ 2100.0 \times 120.0 = 252000.0 \][/tex]

5. Evaluate the third term:

[tex]\(1.5 \times 10^1 = 15.0\)[/tex]

6. Add the result of the multiplication to the third term:

[tex]\[ 252000.0 + 15.0 = 252015.0 \][/tex]

So, the detailed step-by-step solution yields the final answer:

[tex]\[ (2.1 \times 10^3) \times (1.2 \times 10^2) + (1.5 \times 10^1) = 252015.0 \][/tex]