1. Move the decimal point to the right until you have a number between 1 and 10. In this case, we move it three places to the right: 4.21
2. Count the number of places you moved the decimal. We moved it three places.
3. Express the number as a product of the new number and 10 raised to the power of the number of places you moved the decimal. Since we moved the decimal three places to the right, the exponent is negative.
Therefore, the scientific notation of 0.00421 is 4.21 x 10⁻³.
