IGCSE Biology 0610 - 2.2 Size of Specimens

Objective: Convert measurements between millimetres (mm) and micrometres (μm)

Understanding the Relationship

Millimetres (mm) and micrometres (μm) are units of length. A micrometer is a much smaller unit than a millimetre. The relationship between them is:

1 mm = $1000$ μm

1 μm = $0.001$ mm

Conversion Methods

We can convert measurements between mm and μm using the following methods:

• Multiply by 1000 to convert mm to μm.
• Divide by 1000 to convert μm to mm.

Examples

Example 1: Convert 5 mm to μm

To convert 5 mm to μm, we multiply by 1000:

$5 \text{ mm} \times \frac{1000 \text{ μm}}{1 \text{ mm}} = 5000 \text{ μm}$

Example 2: Convert 250 μm to mm

To convert 250 μm to mm, we divide by 1000:

$250 \text{ μm} \times \frac{1 \text{ mm}}{1000 \text{ μm}} = 0.25 \text{ mm}$

Conversion Table

Millimetres (mm)	Micrometres (μm)
0 mm	0 μm
1 mm	1000 μm
2 mm	2000 μm
5 mm	5000 μm
10 mm	10000 μm
25 mm	25000 μm
100 mm	100000 μm

Practice Questions

1. Convert 3.5 mm to μm.
2. Convert 150 μm to mm.
3. A bacterium is 2 μm long. How long is it in mm?
4. A cell is 0.75 mm in diameter. How large is it in μm?

Answers to Practice Questions

1. $3.5 \text{ mm} \times 1000 = 3500 \text{ μm}$
2. $150 \text{ μm} \div 1000 = 0.15 \text{ mm}$
3. $2 \text{ μm} \div 1000 = 0.002 \text{ mm}$
4. $0.75 \text{ mm} \times 1000 = 750 \text{ μm}$