What is the scientific notation for the average size of grass pollen?

What is the scientific notation for the average size of grass pollen?

• A. 2.5 x 10^-5 m
• B. 2.5 x 10^5 m
• C. 2.5 x 10^-3 m
• D. 2.5 x 10^3 m

Answer: (A)

Understanding how to convert tiny lengths from micrometers to meters using scientific notation is what this question tests. Grass pollen grains are about 25 micrometers in diameter. Since 1 micrometer equals 1 × 10^-6 meters, 25 micrometers equals 25 × 10^-6 meters, which simplifies to 2.5 × 10^-5 meters. This is the correct expression for the average pollen size. The other options place the size at magnitudes that don’t match pollen: for example, 2.5 × 10^-3 m is about 2.5 millimeters, which is far too large for pollen, while 2.5 × 10^3 m and 2.5 × 10^5 m are kilometers and tens of kilometers, respectively.

Understanding how to convert tiny lengths from micrometers to meters using scientific notation is what this question tests. Grass pollen grains are about 25 micrometers in diameter. Since 1 micrometer equals 1 × 10^-6 meters, 25 micrometers equals 25 × 10^-6 meters, which simplifies to 2.5 × 10^-5 meters. This is the correct expression for the average pollen size. The other options place the size at magnitudes that don’t match pollen: for example, 2.5 × 10^-3 m is about 2.5 millimeters, which is far too large for pollen, while 2.5 × 10^3 m and 2.5 × 10^5 m are kilometers and tens of kilometers, respectively.