The length and breadth of a rectangular ground is 30 m and 20 m respectively. A boy moves around the ground 5 times early morning everyday. Find the distance covered by him?​

The first-serve percentage of a tennis player in a match is normally distributed with a standard deviation of 4.3%. if a sample of 15 random matches of the player is taken, the mean first-serve percentage is found to be 26.4%. what is the margin of error of the sample mean? a. 0.086% b. 0.533% c. 1.11% d. 2.22%

The anwser cause i do not understand just plez

What is the circumference of a circle with an area of 50.24 cm²?