Question

A hollow discoid (cylindrical) microfossil has an outer diameter of 20 µm, height 10 µm and wall thickness 1 µm. The internal volume that can be occupied by the organism is ________ µm³. (Use π = 3.14) (Round off to one decimal place.)

Hint:

Always subtract wall thickness before calculating internal volume in microfossil geometry problems.

Answer 1

Correct Answer: 2543

Step 1: Formula for cylinder volume.
Volume \( V = \pi r^{2} h \).
Step 2: Calculate internal radius.
Outer radius = 20/2 = 10 µm. Wall thickness = 1 µm. Inner radius = 10 – 1 = 9 µm.
Step 3: Substitute values.
\( V = \pi (9)^{2} (10) = 3.14 \times 81 \times 10 = 2543.4 \, \text{µm}^3. \)
Step 4: Rounding and verification.
Internal volume = 2543.4 µm³ (rounded to one decimal).