 Right, friends, so here is the question. So this question actually tests you to find out the average speed properly. So let's see what this question is all about. So particle moving in a straight line covers half the distance with a speed of 3 meter per second. So the particle is moving in a straight line. So let me draw a straight line first. And then it covers half the distance. So let's say total distance is d. The half distance will be d by 2. So this distance is covered with a speed of 3 meter per second. The other half of the distance is covered in two equal time intervals with a speed of 4.5 and 7.5. So other half is covered in two equal time intervals. So if this is t time, let's say this is point A, point B, this is C, and let's say this is d point. So B to C, the time taken is t, then C to D is also time taken will be t only. And since the speeds are different to cover B to C, the speed is 4.5 meter per second. And to cover C to D, the speed is 7.5 meter per second. Since the speeds are different, B to C distance is not equal to C to D distance. Although the time taken is same. Now what it asks is to find the average speed of the particle during this motion. Now we know that average speed of a particle is what, total distance, total distance covered by the particle divided by what, total time. So total distance, we have assumed that to be equal to small d. Now total time, how will we find out? So for A to B, distance is given, d by 2. So you can find the time by, let's say this is d by 2. So the time will be what, distance divided by the speed. So d by 2 divided by 3. Now I want to find out what is the distance B to C and distance C to D. What I know is B to D distance. This total distance is given as d by 2. So if this distance is, let us say x, that distance will be what, d by 2 minus of x. So the x distance, you can write down that as 4.5 into t, plus 7.5 multiplied by t, this should be equal to d by 2. So from here, you'll get the value of t. The value of t will be d divided by 2 times of 4.5 plus 7.5, which is nothing but 12. So this is t and total time is what, t plus t, which is 2t. So I'll just multiply here with 2 times of small t. That will come out to be d divided by 12. So the average speed comes out to be equal to d divided by d by 6 plus d by 12. So this will be equal to what? Average speed will be equal to 12 into 6 divided by 12 plus 6, which is 18. So 6, 3 is 18 and 3, 4 is 12. So you will get answer here as 4 meter per second. So you can tick option number A to be correct. Thank you.