Question

A train covered first 120 km at a speed of 20 km an hour and then covered the remaining 180 km at a speed of 45 km an hour. Find its average speed​

Answer 1

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 A train covered first 120 km at a speed of 20 km an hour and then covered the remaining 180 km at a speed of 45 km an hour. Find its average speed.

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$\small\tt{Total\:Distance\:=\:120+180=\:300\:km}$

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$\small\tt{Time\: Taken\:For\:the\:first\:120\:km}\\{\small\tt{\:=\:{\cancel\frac{120}{20}}=\:6\:hrs}}$

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$\small\tt{Time\: Taken\:For\:the\:next\:180\:km}\\{\small\tt{\:=\:{\cancel\frac{180}{45}}=\:4\:hrs}}$

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$\small\tt{Total\:Time\:Taken\:=\:6+4\:=\:10\:hrs}$

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$\small\tt\purple{\underline{\boxed{Average\:Speed=\:{\frac{Total\:Distance\: Travelled}{Total\:Time\:Taken}}}}}$

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$\small\tt{Average\:Speed\:=\:{\cancel\frac{300}{10}}}$

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$\small\tt\red{\underline{\boxed{Average\:Speed\:=\:30\:km/hr}}}$

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Answer 2

Step-by-step explanation:

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A train covered first 120 km at a speed of 20 km an hour and then covered the remaining 180 km at a speed of 45 km an hour. Find its average speed?

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$total \: distance \: travelled = 120 + 180 = 300km$

$time \: taken \: for \: the \: first \: 120 \: km$

$= \frac{120}{20} = 6 \: hrs$

$time \: taken \: for \: the \: next \: 180 \: km$

$= \frac{180}{45} = 4hrs$

$time \: taken = 6 + 4 = 10 \: hrs$

$average \: speed = \frac{total \: distance \: travelled}{total \: time \: taken}$

$average \: speed = \frac{300}{10}$

$average \: speed = 30 \: km \: per \: hours$