I have this question: A particle moving in a straight line covers half the distance with speed 3m/s. The other half of the distance is covered in two equal time intervals with speed 4.5m/s and 7.5m/s respectively. The average speed of the particle during this motion is what? (4m/s - Ans) I did so by taking the total distance as x, half the distance as x/2 and the other half which was further divided in two equal parts as x/4 and x/4. Then, as I know the speeds, I calculated the time which was: x/6,x/18 and x/30 respectively. Now since it's ' average speed = total distance/total time I did, x/[x/6+x/18+x/30] which came out to be 23/90 or 3.9 m/s The real solution showed the answer to be 4.0m/s and I didn't get the method. So, can 3.9m/s be rounded off as 4.0m/s? Correct me Login To add answer/comment