Back to Ganita Prakash: Class 7 Mathematics, Par...BackConcept

Read A Graph Like A Detective: Rockets And Sunshine

Read complex graphs in two steps, identify what is shown and then infer, and check which statements the data can support.

6 micro-lessons

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The 2-Step Method

Step 1: identify what is given. Step 2: infer from what is given.

Rockets (Textbook pp. 115–116)

Every space mission is launched by a rocket: probes like Chandrayaan-3 (ISRO, 2023) and Voyager-1 (NASA, 1977), satellites like Aryabhata (ISRO, 1975) and Sputnik-1 (1957), and crews to the International Space Station.

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Rocket Launches 2021–2023

Applying the 2-step method to a graph of rocket launches.

Problem. The book's graph shows rocket launches worldwide by organisation. What does it tell us? (Textbook pp. 116–117; data from Bryce Tech via Statista)

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Justified or Not?

A claim is justified only if the graph's data supports it.

Before you agree with a claim

Does the graph show this quantity, for these groups and these years?

Estimates from bar lengths are approximate: say 'about'.

Claims about things outside the graph (other countries, other years, 'the world') cannot be justified from it.

Which Statements Hold?

Test the book's six statements about rocket launches.

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(a) All organisations launched more rockets than in previous years. (Textbook p. 118)

Summer and Winter at Once

Use the 2-step method to work out where the two cities are.

Read the daylight graph

Textbook pp. 118–121. The tables give the hours of daylight in each month for two cities (the Sun at least partly above the horizon):

| | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |---|---|---|---|---|---|---|---|---|---|---|---|---| | City 1 | 210 | 257 | 372 | 441 | 536 | 564 | 555 | 465 | 394 | 310 | 222 | 186 | | City 2 | 459 | 384 | 381 | 327 | 304 | 276 | 295 | 318 | 369 | 409 | 435 | 468 |

The chart above shows the average daylight hours per day: each monthly total ÷ the number of days in that month. Use the 2-step method.

Step 1: Identify*

Scale, organisation, highest and lowest months.

Step 2: Infer*

How does daylight change over the year in each city?

Where might these cities be?*

Why would their patterns be opposite?

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