One day Andrew goes from his home to his school at a speed of 20 km/hr but on finding that it was holiday in school, he plans to have party with friends at a restaurant which is situated exactly at midpoint of his way from home to school so he starts back and reaches the restaurant at speed of 40 km/hr without wasting any time at school. Find the average speed of Andrew from home till he reaches restaurant after visiting school.

Let the Distance from Home to School be D km.

Speed of Andrew from Home to School = 20km/hr

Thus Time taken to reach school from home = Distance / speed = \(\frac{D}{20}\)

Restaurant is exactly at midpoint from home to school, therefore Distance from school to restaurant = \(\frac{D}{2}\)km

Speed of Andrew from School to Restaurant = 40km/hr

Time taken to reach restaurant from school = \(\frac{D}{2}\)/40 = \(\frac{D}{80}\)

Average Speed = Total Distance Traveled / Total Time Taken

Average Speed of Andrew from Home till Restaurant = D + \(\frac{D}{2}\) / \(\frac{D}{20}\) + \(\frac{D}{80}\) = \(\frac{2D + D}{2}\) / \(\frac{4D + D}{80}\) = \(\frac{3D}{2}\)/\(\frac{5D}{80}\) = \(\frac{3}{2}\) x \(\frac{80}{5}\) =

24km/hr Answer A..._________________

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