A man walks with speed 15 km/hr instead of 12 km/hr and covers 20 km more distance. Find the distance covered by him with speed 15 km/hr.A 50 km B 60 km C 70 km D None of these

Let's solve this step by step:

Step 1: First, we need to find out how much time he would have spent if he was walking at a speed of 12 km/hr. We know that time = distance/speed. But in this case, we don't know the original distance. We only know that he covered 20 km more. So, let's assume the original distance to be 'x' km. Therefore, the time taken at 12 km/hr speed would be x/12 hours.

Step 2: Now, we know that he covered 20 km more at a speed of 15 km/hr. So, the time he spent walking at this speed is (x+20)/15 hours.

Step 3: According to the problem, the time spent in both cases should be the same. So, we can set up the equation x/12 = (x+20)/15.

Step 4: Solving this equation, we get x = 60 km. This is the original distance he would have covered at a speed of 12 km/hr.

Step 5: But the question asks for the distance he covered at a speed of 15 km/hr. So, we add the extra 20 km he covered to the original distance. Therefore, the distance covered at 15 km/hr is 60 km + 20 km = 80 km.

So, the answer is 80 km, which is not in the given options. Therefore, the correct answer is D: None of these.