An individual's red blood cell (RBC) count and haemoglobin levels vary depending on their health and environment. The table below shows the average RBC count and haemoglobin concentration of a healthy adult and an adult suffering from iron-deficiency anaemia.
| Group | Average RBC Count (1012 cells/dm310^{12} \text{ cells/dm}^31012 cells/dm3) | Average Haemoglobin Concentration (g/dm3\text{g/dm}^3g/dm3) |
|---|---|---|
| Healthy Adult | 5.0 | 150 |
| Adult with Anaemia | 3.2 | 96 |
Calculate the percentage decrease in the average haemoglobin concentration of the adult with anaemia compared to the healthy adult.
Explain how a lower haemoglobin concentration causes the symptom of extreme tiredness.