Question

question 74 (1 point)
expression of 21001 in scientific notation is:

1. $21.001 \times 10^3$
2. $2.1001 \times 10^4$
3. $210.01 \times 10^2$
4. $2.1001 \times 10^5$

Explanation:

Step1: Recall scientific notation rule

Scientific notation is $a \times 10^n$, where $1 \leq |a| < 10$ and $n$ is an integer.

Step2: Analyze 21001

To write 21001 in scientific notation, we move the decimal point 4 places to the left to get $a = 2.1001$, so $n = 4$. Thus, $21001 = 2.1001 \times 10^4$.

Step3: Check options

• Option 1: $21.001 \times 10^3$ has $a = 21.001$ (not between 1 and 10), invalid.
• Option 2: $2.1001 \times 10^4$ matches our calculation.
• Option 3: $210.01 \times 10^2$ has $a = 210.01$ (not between 1 and 10), invalid.
• Option 4: $2.1001 \times 10^5$ would be 210010, not 21001.

Answer:

1. \( 2.1001 \times 10^4 \)