Chapter 6 of 7

86%

Tamil Nadu (TNBSE)Class 8 Mathematics★ 5-8 marks in the TN Class 8 annual exam through MCQs, pie-chart and graph problems

Statistics

Samacheer Kalvi (TN State Board) Class 8 Maths Chapter 6, Statistics. Organising data in a frequency distribution table and representing it with histograms, frequency polygons and pie diagrams. Notes with formulas, worked examples, common mistakes, book-back practice and quick revision.

⏱ 16 min readEasy difficulty✓ Free · NCERT-aligned

Worksheet

Podcast

Listen as a conversation

A teacher & a student talk through the chapter — in your language.

Mind Map

The chapter at a glance

Every concept and exam-favourite branch — revisable in 5 minutes.

…

Study Guide

Night-before notes

Key points, glossary and the questions most likely to show up.

…

VocabularyBuild your vocabularyLexiGenome mines the key words and schedules them with spaced repetition.Mine words →

By the end of this chapter you'll be able to…

1Build a frequency distribution table
2Draw and read histograms
3Construct frequency polygons
4Compute sector angles for pie charts
5Choose the right graph for the data

💡

Why this chapter matters

Statistics teaches how to organise and picture data using tables, histograms, frequency polygons and pie charts. Pie-chart angle calculations are easy, reliable marks in the TN Class 8 exam.

Before you start — revise these

A 5-minute refresher here will save you 30 minutes of confusion below.

🔗

Class 7 — Data handling

Bar graphs and averages.

Statistics — Class 8 Maths (Samacheer Kalvi)

TN State Board (Samacheer Kalvi) Class 8 Mathematics, Chapter 6. Organising and picturing data.

1. About this chapter

This chapter covers organising data in a frequency distribution table and representing it using histograms, frequency polygons and pie diagrams.

2. Organising data

Frequency = how many times a value occurs.
A frequency distribution table groups data into classes with their frequencies.

3. Graphical representation

Histogram: bars with no gaps, used for continuous (grouped) data; bar heights show frequency.
Frequency polygon: join the mid-points of the tops of the histogram bars.
Pie diagram: a circle divided into sectors; sector angle = (value / total) × 360°.

4. Worked examples

Example 1. In a budget, food is ₹3000 out of ₹12000. Find the sector angle for food in a pie chart. = (3000/12000) × 360° = ¼ × 360° = 90°.

Example 2. What graph is used for continuous grouped data? A histogram (bars with no gaps).

Example 3. A frequency polygon is formed by joining which points? The mid-points of the tops of the histogram bars.

5. Common mistakes

Mistake: Leaving gaps between histogram bars. Fix: Histograms have no gaps (data is continuous).
Mistake: Wrong sector angle in a pie chart. Fix: angle = (value / total) × 360°.
Mistake: Using a histogram for discrete categories. Fix: Use a bar graph for discrete data; histograms are for grouped/continuous data.

6. Practice (book-back style)

Define frequency.
Write the formula for the sector angle in a pie chart.
A subject scores 90 out of 360 total marks shown in a pie chart — find its angle.
Which graph has bars with no gaps?
How is a frequency polygon drawn?

7. Answer key

The number of times a value occurs in the data.
Sector angle = (value / total) × 360°.
(90/360) × 360° = 90°.
A histogram.
By joining the mid-points of the tops of the histogram bars.

8. Quick revision

Chapter 6 · frequency, histogram, polygon, pie chart.
Frequency distribution table groups data with frequencies.
Histogram: bars with no gaps (continuous data).
Frequency polygon: join mid-points of bar tops.
Pie chart sector angle = (value / total) × 360°.

Key formulas & results

Everything you need to memorise, in one card. Screenshot this for revision.

Pie-chart sector angle

(value / total) × 360°

Fraction of the whole circle.

Histogram

bars with no gaps (continuous data)

Height = frequency.

Frequency polygon

join mid-points of bar tops

Built from a histogram.

⚠️

Common mistakes & fixes

These are the exact errors that cost students marks in board exams. Read them once, save yourself the trouble.

WATCH OUT

✗ Leaving gaps between histogram bars

✓ Histograms have no gaps (data is continuous).

WATCH OUT

✗ Wrong sector angle in a pie chart

✓ Angle = (value / total) × 360°.

WATCH OUT

✗ Using a histogram for discrete categories

✓ Use a bar graph for discrete data; histograms are for grouped data.

NCERT exercises (with solutions)

Every NCERT exercise from this chapter — what it covers and how many questions to expect.

Multiple choice questions

MCQs on frequency, histograms and pie charts.

Questions

Pie-chart problems

Compute sector angles and read pie charts.

Questions

Graph construction

Draw histograms and frequency polygons.

Questions

Practice problems

Try each one yourself before tapping "Show solution". Active recall > rereading.

Q1EASY· Concept

Define frequency.

▶ Show solution

The number of times a value occurs in the data.

Q2EASY· Recall

Write the formula for the sector angle in a pie chart.

▶ Show solution

Sector angle = (value / total) × 360°.

Q3EASY· Numerical

A subject scores 90 out of 360 total marks shown in a pie chart — find its angle.

▶ Show solution

(90/360) × 360° = 90°.

Q4EASY· Concept

Which graph has bars with no gaps?

▶ Show solution

A histogram.

Q5EASY· Concept

How is a frequency polygon drawn?

▶ Show solution

By joining the mid-points of the tops of the histogram bars.

Q6MEDIUM· Numerical

In a budget, food is ₹3000 out of ₹12000. Find the pie-chart sector angle for food.

▶ Show solution

(3000/12000) × 360° = 90°.

5-minute revision

The whole chapter, distilled. Read this the night before the exam.

•Chapter 6 of Samacheer Kalvi Class 8 Mathematics.
•Frequency = number of occurrences; tables group data.
•Histogram: bars with no gaps (continuous data).
•Frequency polygon: join mid-points of bar tops.
•Pie-chart sector angle = (value / total) × 360°.
•Choose the graph to suit the data type.

Tamil Nadu (TNBSE) marks blueprint

Where the marks come from in this chapter — so you can plan your prep.

Typical chapter weightage: 5-8 marks across MCQ, pie-chart and graph problems

Question type	Marks each	Typical count	What it tests
MCQ	1	1-2	Frequency, graph types
Pie Chart	2-3	1-2	Sector angle calculations
Graph	2-3	1	Histogram / polygon

Prep strategy

Build frequency tables from raw data
Use the sector-angle formula
Draw histograms without gaps
Join mid-points for the polygon

Where this shows up in the real world

This chapter isn't just an exam topic — it lives in the world around you.

Budgets

Pie charts show how money is shared across expenses.

Reports

Histograms summarise marks, heights and measurements.

Surveys

Frequency tables organise survey responses.

Exam strategy

Battle-tested tips from teachers and toppers for this chapter.

Use (value/total) × 360° for pie charts
Draw histogram bars touching
Join mid-points for the polygon
Match graph type to the data

Going beyond the textbook

For olympiad aspirants and curious learners — topics that build on this chapter.

Construct a pie chart for a five-category data set.
Compare a histogram and a frequency polygon of the same data.

Where else this chapter is tested

CBSE board isn't the only one — other exams test this chapter too.

TN Class 8 Annual ExamHigh

Foundation / NMMS MathematicsMedium

School unit testsHigh

AI helpers for this chapter

Generate more practice on the fly, or have the chapter explained at a different level.

⚡

Generate 5 more questions

Fresh MCQs + short-answer items based on this chapter, plus answer keys.

🧠

Explain at a different level

Re-explain the chapter at the level you actually want.

📝 My notes

Saved on this device — sign in to sync · how this works

0/600

Questions students ask

The real ones — pulled from the Q&A community and tutor sessions.

A bar graph shows discrete categories with gaps between bars; a histogram shows continuous grouped data with bars touching (no gaps).

Because a full circle is 360°, and each category gets a share of that circle proportional to its value.

Practice more, ask doubts, find a tutor

Tamil Nadu (TNBSE) Class 8 mock tests

Tamil Nadu (TNBSE) Class 8 PYQs

Ask in Q&A

Mathematics flashcards

Related chapters

Students who read Statistics usually read these next.

Numbers

Samacheer Kalvi (TN State Board) Class 8 Maths Chapter 1, Numbers. Rational numbers and their properties, square roots, cubes and cube roots, and exponents and powers (laws of exponents). Notes with formulas, worked examples, common mistakes, book-back practice and quick revision.

Measurements

Samacheer Kalvi (TN State Board) Class 8 Maths Chapter 2, Measurements. Area and perimeter of combined plane figures, the circle (length of an arc and area of a sector), and three-dimensional shapes (nets and views of solids). Notes with formulas, worked examples, common mistakes, book-back practice and quick revision.

Algebra

Samacheer Kalvi (TN State Board) Class 8 Maths Chapter 3, Algebra. Multiplication and division of algebraic expressions, algebraic identities (including cubic identities), factorisation, and linear equations in one variable. Notes with formulas, worked examples, common mistakes, book-back practice and quick revision.

Life Mathematics

Samacheer Kalvi (TN State Board) Class 8 Maths Chapter 4, Life Mathematics. Percentage, profit and loss, discount, simple and compound interest, direct and inverse proportion, and time and work. Notes with formulas, worked examples, common mistakes, book-back practice and quick revision.

🧑‍🏫