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எங்கள் ஆசிரியர்களுடன் 1-ஆன்-1 ஆலோசனை நேரத்தைப் பெறுங்கள். டாப்பர் ஆவதற்கு நாங்கள் பயிற்சி அளிப்போம்

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Subjects
Science CBSE
Class 9
Motion
Textbook questions

3. Exercises III

Exercise condition:

5 m.

Abdul, while driving to school, computes the average speed for his trip to be \(20\ kmh^{–1}\). On his return trip along the same route, there is less traffic and the average speed is \(30\ kmh^{–1}\). What is the average speed for Abdul’s trip?

The formula to calculate the average speed,

\(=\ \frac{Total\ distance\ travelled}{Total\ time\ taken}\)
\(=\ \frac{Total\ displacement}{Total\ time\ taken}\)
\(=\ {Total\ displacement} \times {Total\ time\ taken}\)
\(=\ {Total\ distance\ travelled} \times {Total\ time\ taken}\)

Consider,

Distance travelled to reach the school \(=\) Distance travelled to reach home \(=\) \(d\)

Time taken to reach school from home \(=\ t_1\)

Time taken to reach home from school \(=\ t_2\)

Average speed of Abdul while going to school,

\(=\ {d} \times {t_1}\)
\(=\ \frac{d}{t_2}\)
\(=\ \frac{d}{t_1}\)
\(=\ {d} \times {t_2}\)

Average speed of Abdul while returning to home,

\(=\ {d} \times {t_2}\)
\(=\ \frac{d}{t_1}\)
\(=\ {d} \times {t_1}\)
\(=\ \frac{d}{t_2}\)

Abdul’s average speed for the entire trip \(=\) \(kmh^{-1}\)

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