A student calculates the magnification of a drawing of a cell.
The drawing is 36 mm long. The actual cell is 12 μm12\ \mu\text{m}12 μm long.
The student writes: magnification =36÷12=×3= 36 \div 12 = \times 3=36÷12=×3
Which statement gives the correct magnification and the student's error?
×300\times 300×300; one zero was lost when converting millimetres to micrometres
×0.33\times 0.33×0.33; the actual length should have been divided by the image length
×3000\times 3000×3000; the image length was divided by the actual length the wrong way round
×3000\times 3000×3000; both lengths should have been converted to the same unit first
130 exam-style questions on OCR GCSE Biology 1.1 Cell structures, covering 1.1.1 Viewing cells with light microscopes, 1.1.2 Sub-cellular structures and functions, and 1.1.3 Electron microscopy and resolution. Each one has a worked solution and a mark scheme showing where the marks go.