Example 7.2. From the following table, estimate the number of students who obtained marks between 40 and 45: Marks 30-40 40-50 5060 60-70 70-80 No. of students : 31 42 51 35 31 435 Example 7.2. From the following table, estimate the number of students who obtained marks between 40 and 45: Marks 30-40 40-50 5060 60-70 70-80 No. of students : 31 42 51 35 31 435