A school has four sections in Class XII having 50, 39, 42, 48 students of the four section. In a mathematics test the average marks were 60, 55, 57 and 48 respectively. What was the overall average of the marks per student?

A class of 50 students belonging to the Kindergraten is divided in two sections A and B , having students in the ratio 2:3 respectively. The average weight of the students of the entire calss is 40 Ibs. The average weight of the students of section A is 2 Ibs . less than that of the students B. What is the average weight of the students of section B ?

The marks of 10 students in a class are 38, 70, 48,34 ,42, 55 63, 46, 54,44. Find the standard deviation of these marks.

A student obtained 62 and 48 marks in the first and secound examinations of class XI. Find the minimum marks he should get in annul examination to have an average of at least 60 marks.

The line of regression marks in economics (X) for marks in mathematics (Y) for a class of 50 students is 3y - 5x+180 = 0. Average score in mathematics is 44 and variance of marks in economics is 9/16th , of variance of marks in mathematics. Find the average score in economics and also the coefficient of correlation between marks in economics and mathematics.

A teacher wanted to analysis the performance of two sections of students in a mathematics test of 100 marks. Looking performance, she found that a few students got under 20 marks and a few got 70 marks or above. So she decided to group them into intervals of varying sizes as follows : 0-20, 20-30, ....., 60-70, 70-100. Then she formed the following table : |{:("Marks"," Number of students"),(0-20," 7"),(20-30," 10"),(30-40," 10"),(40-50," 20"),(50-60," 20"),(60-70," 15"),(70-"above"," 8"),("Total"," 90"):}| (i) Find the probability that a student obtained less than 20% in the mathematics test. (ii) Find the probability that a student obtained marks 60 or above .