The marks obtained by a student of Class XI in first and second terminal examination are 62 and 48, respectively. Find the minimum marks he should get in the annual examination to have an average of at least 60 marks.

The marks obtained by a student of class XI in the first and second terminal examination are 62 and 48 respectively. Find the minimum marks he should get in the annual examination to have an average of at least 60 marks .

Ravi obtained 70 and 75 marks in first two unit test. Find the minimum marks he should get in the third test to have an average of at least 60 marks.

Ravi obtained 70 and 75 marks in first two unit tests. Find the minimum number should get in the third test to have an average of at least 60 marks.

To receive Grade ‘A’ in a course, one must obtain an average of 90 marks or more in five examinations (each of 100 marks). If Sunita’s marks in first four examinations are 87, 92, 94 and 95, find minimum marks that Sunita must obtain in fifth examination to get grade ‘A’ in the course.

The marks (out of 100) obtained by a group of students in a science test are 85,76,90,85,39,48,56,95,81 and 75. Find the : Mean marks obtained by the group.

The data regarding marks obtained by 48 students of a class in a class test is given below. Calculate the modal marks of students.

The marks (out of 100) obtained by a group of students in a science test are 85,76,90,85,39,48,56,95,81 and 75. Find the : Range of the marks obtained.

The marks (out of 100) obtained by a group of students in a science test are 85,76,90,85,39,48,56,95,81 and 75. Find the : Highest and the lowest marks obtained by the students.

In a class, 9 students have secured the following marks in a vocabulary test. Find the median. Marks: 6, 12, 8, 13, 7, 11, 9, 7, 10

(a) A point object is placed in front of a double convex lens ( of refractive index n = n_(2) // n_(1) with respect to air ) with its spherical faces of radii of curvature R_(1) and R_(2) . Show the path of rays due to refraction at first and subsequently at the second surface to obtain the formation of the real image of the object. Hence obtain the lens-maker's formula for a thin lens. A double convex lens having both faces of the same radius of curvature has refractive index 1.55. Find out the radius of curvature of the lens required to get the focal length of 20cm.