Question

a boat while going downstream ina river covered a distance of 50 miles at an avarage speed of 60 miles per hours.while returning because of water resistance it took 1 hours 15 minute to cover the same distance .what was the average speed during the whole journey​

Answer 1

Answer:

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Answer 2

Given :

Distance covered  = 50 miles

Average speed = 60 miles/hr

Time for upstream = 1 hour 15 minutes

To find : Average speed = ?

Solution :

Distance traveled = 50 miles

Time = $1\dfrac{15}{60}=1\dfrac{1}{4}=\dfrac{5}{4}$

So, Speed would be

$\dfrac{Distance}{time}=speed\\\\speed=\dfrac{50}{\dfrac{5}{4}}\\\\speed=\dfrac{50\times 4}{5}\\\\Speed=10\times 4\\\\Speed=40\ miles/hr$

So, Average speed would be

$\dfrac{2xy}{x+y}=\dfrac{2\times 60\times 40}{60+40}=\dfrac{2\times 2400}{100}=2\times 24=48\ miles/hr$

Hence, the required average speed = 48 miles/hr.