Answer :

To write the average width of a human hair, 0.0018 centimeters, in scientific notation, follow these steps:

1. Identify the Decimal Point: The given number is 0.0018.

2. Move the Decimal Point: To express the number in scientific notation, you need to move the decimal point so that there is only one non-zero digit to the left of the decimal. For 0.0018, you need to move the decimal point 3 places to the right to get 1.8.

3. Count the Moves: Moving the decimal point 3 places to the right gives 1.8. Since you moved the decimal point to the right, this movement represents a negative exponent.

4. Determine the Exponent: The number of places you moved the decimal point will be the exponent of 10 in the scientific notation. Here, you moved it 3 places, so the exponent will be -3.

5. Construct the Scientific Notation: Write the resulting number as a product of the digit term and an appropriate power of 10. In this example, you get [tex]\(1.8 \times 10^{-3}\)[/tex].

Therefore, the average width of a human hair expressed in scientific notation is [tex]\( 1.8 \times 10^{-3} \)[/tex] cm.