A man goes to Lucknow from Kanpur at a speed of 36 km/hr and returns to Kanpur at speed of 45 km/hr, through the same route. What is his average speed (in km/hr) of the entire journey?

Correct option is D

Given:

Speed Kanpur →Lucknow = 36 km/h;

return =45 km/h; distances equal.

Formula Used:
Average speed for equal distances =$$\dfrac{2ab}{a+b}$$​​

Solution:
​$$\text{Avg speed}=\frac{2\times36\times45}{36+45}$$​​
​$$=\frac{3240}{81}=40\ \text{km/h}.$$​​

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