Explanation

The speed of the bus going from Islamabad to Murree was 100 km/h,

while the speed of the bus was 130 km/h when coming back from Murree to Islamabad.

200km/h was the average speed of is the whole journey

for time using this formula

Using speed = Time/ Distance​

Time= speed/  distance

for average speed in the whole journey using this formula:

Now, Average speed =  Time  (tot)/ Distance  (tot)

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