A suspension contains 2.4×10^9 cells in 3.0 mL. What is the number of cells per millilitre?

A suspension contains $2.4 \times 1 0^{9}$ cells in 3.0 mL. What is the number of cells per millilitre?

medium 2 marks Class 9 · Science · The Fundamental Unit of Life

Answer

8.0×10^8 cells/mL

The correct answer is 8.0×10^8 cells/mL — Answer: $8.0 \times 1 0^{8}$ cells/mL.

Total cells = $2.4 \times 1 0^{9}$ .
Volume of suspension = 3.0 mL.
Number of cells per mL = total cells ÷ volume = $\frac{2.4 \times 1 0 ^{9}}{3.0}$ .
Simplify: $\frac{2.4}{3.0} = 0.8$ , so $0.8 \times 1 0^{9} = 8.0 \times 1 0^{8}$ .
Answer: $8.0 \times 1 0^{8}$ cells/mL.

Common mistake: Incorrectly adding or dividing values

Concept tested: Cell density