The table above shows the score of a group of students in a test. If the average is 3.5, find the value of x

I.    Rectangular bars of equal width
II.    The height of each rectangular bar is proportional to the frequency of the corresponding class interval
III.    Rectangular bar have common sides with no gaps in between
A histogram is described completely by

The weight of 10 pupils in a class are 15kg, 16kg, 17kg, 18kg, 16kg, 17kg, 17kg, 17kg,18kg and 16kg. What is the range of this distribution?

The mean age of a group of students is 15 years. When the age of a teacher is 45years old is added to the ages of the students, the mean of their ages becomes 18 years. Find the number of students in the group.

The pie chart above the distribution of the crops harvested from a farmland in al year. If 3000 tonnes of millet is harvested, what amount of beans is harvested?

Find the mean deviation of 1, 2, 3 and 4

The histogram above shows the ages of the victims of pollution. How many people were involved in the pollution?

The mean of the numbers 3, 6, 4,x, and 7 is 5.  Find the standard deviation.