Find different sets of $6$ different numbers between $10$ and $30$ with the mean as $15$.

Find different sets of $6$ different numbers between $10$ and $30$ with the mean as $25$.

The table below shows the children in a class, sorted according to their height. What is the mean height of a child in this class?

The teachers in a university are sorted according to their ages, as shown below. What is the mean age of a teacher in this university?

The table below shows children in a class sorted according to their weights. The mean weight is calculated as $26$ kilograms. How many children have weights between $23$ and $25$ kilograms?