A car travels at 54 km/hr for first 20 secs , 36 km/hr for next 30 secs and finally 18 km/hr for next 10 secs. Find its average speed.

Sure, let's calculate the average speed step by step.

Step 1: Convert all speeds to m/s 1 km/hr = 5/18 m/s So, 54 km/hr = 54 * (5/18) = 15 m/s 36 km/hr = 36 * (5/18) = 10 m/s 18 km/hr = 18 * (5/18) = 5 m/s

Step 2: Calculate the distance covered at each speed Distance = Speed * Time So, for the first 20 seconds, the car travels 15 m/s * 20 s = 300 m For the next 30 seconds, the car travels 10 m/s * 30 s = 300 m For the final 10 seconds, the car travels 5 m/s * 10 s = 50 m

Step 3: Calculate the total distance and total time Total distance = 300 m + 300 m + 50 m = 650 m Total time = 20 s + 30 s + 10 s = 60 s

Step 4: Calculate the average speed Average speed = Total distance / Total time = 650 m / 60 s = 10.83 m/s

So, the average speed of the car is 10.83 m/s.