1.

A man covered a certain distance at an average speed of 100 km/hr and came back at the speed of 80 km/hr. find the average speed of the man during the whole journey?  1. \(22\frac{2}{9}\) km/hr2. \(44\frac{4}{9}\) km/hr3. \(88\frac{8}{9}\) km/hr4. 45 km/hr5. 55 km/hr

Answer» Correct Answer - Option 3 : \(88\frac{8}{9}\) km/hr

Given:

Speed while going (S1) = 100 km/hr

Speed while returning (S2) = 80 km/hr

Formula used:

Average speed = 2S1S2/(S1 + S2)

Calculation:

Average speed =  \(\frac{{2 \times 100\times 80}}{{100 + 80}}\)  

⇒ 16000 / 180

⇒  \(88\frac{8}{9}\)

∴ The average speed of the man during the whole journey is \(88\frac{8}{9}\) km/hr



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