When two or more waves meet, they interact with each other. The interaction of waves with other waves is called wave interference. Wave interference may occur when two waves that are traveling in opposite directions meet. The two waves pass through each other, and this affects their amplitude.
You must first convert minutes to seconds so 10*60=600
Then multiply the number of seconds by the speed so 600*2=1200 m
The results may differ due to resistive forces that may be affecting the system by decelerating it or any other external forces that might accelerate it a bit.Or the timing could be a little inaccurate.