A scientist estimated the number of red blood cells in a sample of blood.
The blood was diluted 200 times. A drop of the diluted blood was placed on a counting slide. Each square on the counting slide holds 0.004 mm3 of liquid.
The scientist counted the red blood cells in five squares.
The Table shows the results.
Table
| Square | Number of red blood cells |
|---|---|
| 1 | 110 |
| 2 | 96 |
| 3 | 104 |
| 4 | 98 |
| 5 | 92 |
Calculate the mean number of red blood cells in one square.
Calculate the number of red blood cells in 1 mm3 of the undiluted blood. Give your answer in standard form.
An adult has 5 dm3 of blood.
1 dm3=1×106 mm31\ \text{dm}^3 = 1 \times 10^{6}\ \text{mm}^31 dm3=1×106 mm3
Calculate the total number of red blood cells in the blood of this adult. Give your answer in standard form.
Suggest why the blood was diluted before the red blood cells were counted.
48 exam-style questions on Edexcel GCSE Biology 1.2 Number, size and scale, covering 1.2.1 Number, size and scale with estimations and 1.2.2 Quantitative units in relation to cells. Each one has a worked solution and a mark scheme showing where the marks go.