The fraction in the question text appears corrupted as 83/1. Using the implied distance of 60 km at 100 km/h (same as q5565):<br><br>
&bull; Time at 100 km/h: 60 ÷ 100 = 0.6 h<br>
&bull; Time at 75 km/h: 90 ÷ 75 = 1.2 h<br>
&bull; Total time = 0.6 + 1.2 = 1.8 h<br>
&bull; Average speed = 150 ÷ 1.8 = 83.33... &asymp; 83 km/h<br><br>
Final Answer: 83 km/h