A laboratory spins 40 mL of blood. The formed elements make up 45% of it, and the red cell count is…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A laboratory spins mL of blood. The formed elements make up of it, and the red cell count is million in each mm³.
- What is the volume of the plasma?
- What is the volume of the formed elements?
- How many red cells are in the sample, in billions?
Need a reminder? The key ideaShow
Blood is about plasma and formed elements. A healthy adult has to million red cells in each mm³. The blood holds to g of haemoglobin in each mL in a woman and to g in a man. There are to white cells in each mm³. One mL is mm³. The white cells, from most to least: neutrophils, lymphocytes, monocytes, eosinophils, basophils.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Sample: mL. Formed elements: . Red cell count: million per mm³.
Plan. Use the shares for the volumes. Then change the count from mm³ to mL.
Step 1. Plasma. of the sample. mL.
Step 2. Formed elements. mL. Check: mL.
Step 3. Red cells. In mL there are mm³, so million billion. For mL: billion.
Answer: mL; mL; billion red cells.
Check. The two volumes add up to the sample.
Watch out. The count is for one mm³, not for one mL. Forgetting the factor of gives an answer that is a thousand times too small.
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