To find out the concentratin of `SO_2` in the air (in parts per million, i.e., ppm), the data was collect for 30 localities in a certain city and is presented below.

Find the mean concentration of `SO_2` in the air.

To find out the concentration of SO_(2) in the air (in parts per million , I . e., ppm) , the data was collected for 30 localities in a certain city and is presented below :

A survey was conducted by a group of students as a part of their environment awareness programme, in which they collected the following data regarding the number of plants in 20 houses in a locality. Find the mean number of plants per house.

A survey was conducted by a group of students as a part of their environment awareness programme , in which they collected the follwing data regarding the number of plants in 20 houses in a locality . Find the mean number of plants per house . {:("Number of plants","Number of houses"),(0-2,1),(2-4,2),(4-6,1),(6-8,5),(8-10,6),(10-12,2),(12-14,3):}

A survey was conducted by a group of students as a part of their environmental awareness programme, in which they collected the following data regarding the number of plants In 20 houses in a locality. Find the mean number of plants per house.

A string 25 cm long and having a mass of 2.5g is under tension. A pipe closed at one end is 40 cm long. When the string is set vibrating in its firsy overtone and the air in the pipe in its fundamental frequency, 8 beats per sec are heard. It is observed that decreasing the tension in the string decreases the beat frequency. If the speed of sound in air is 320 m/s, find the tension in the string.