A blood sample has a haematocrit of 42 %. If the sample is 5.0 mL, what volume of plasma does it contain, in mL, to one decimal place?

2.9 (answers within ±0.1 count)

Plasma is $100 - 42 = 58\%$, so $5.0 \times 0.58 = 2.9$ mL. Plasma is mostly water but carries proteins, nutrients, wastes and hormones, it is the transport medium the whole tissue exists to move.