Topic summary · IGCSE handout
Histograms summary
Histograms use frequency density when class widths vary: area of each bar represents frequency.
Files: 33_histograms_handout.pdf · 33_histograms_handout_answers.pdf · free public downloads · diagrams in the PDFs
Key learning points
- Frequency density = frequency ÷ class width.
- Unequal widths still work if you use density on the vertical axis.
- Estimate frequencies from areas when reading a drawn histogram.
Worked example 1 — Frequency density
Width , frequency . FD?
Working
FD = frequency ÷ width.
Worked example 2 — Area equals frequency
FD , width . Frequency?
Working
Bar area = frequency.
Worked example 3 — Unequal classes
Why use frequency density?
Working
Widths differ.
Scaffolded Learning Sheet and answers (PDFs)
This page is a short, searchable overview for revision and search engines. Use the Scaffolded Learning Sheet first, then the Answers PDF for a full written solution. The printable PDFs remain the main classroom resource.