Visualising Data

Class 7 Maths · Chapter 13: Connecting the Dots… · NCERT Ganita Prakash section P2 5.3

Learn

Pictures make data easier to understand. To compare the monthly price of tomatoes in two towns, draw the two bars for each month side by side in two colours: a clustered (double) bar graph. Patterns or dots inside the bars help readers who cannot tell colours apart.

Step 1: identify what is given. How is the graph organised (what is on each line)? What is the scale (here 1 unit = 10)? What patterns show (prices rising through the year)?

Step 2: infer. Interpret each observation: Town P is costlier in Jan, Feb, Apr and Jun; Town Q in Mar and May. Only make claims the data supports: the graph says nothing about why, or about other towns. A graph of daylight hours in two cities, one rising to June and one falling, tells us they are in opposite hemispheres.

Graphs appear everywhere: runs per over for two cricket teams, rocket launches by different space agencies year by year, speeds of animals. Read the title, labels, scale and key first; then compare, find totals or averages, and spot trends like "increasing every year".

Explore: draw a bar graph.

1. Votes: Cricket 35, Chess 15, Kabaddi 25, Hockey 10. Set each bar.

Remember

• A double bar graph puts two bars per category side by side to compare two groups.
• Read a graph in two steps: identify what is given, then infer only what it supports.

Quick check

In a double bar graph with scale 1 unit = 5 runs, a bar reaches 3 units. How many runs is that?

1. 15
2. 3
3. 8
4. 5

Think about it

Daylight in City 1 peaks at about 18 hours in June; in City 2 it is lowest then. What does that suggest?

Practice

Practise with fresh questions at three levels (easy, medium, hard), some answered hands-on, with hints and worked answers. Get 4 of your last 5 right to finish the topic.