23.) The mean marks of a class of 40 students are 50. If the mean of f

1.	23.) The mean marks of a class of 40 students are 50. If the mean of first 20 students are 56 and themean marks of last 20 students are 48, find the marks of the 20th student.
Answer» Mean marks of 40 students = 50 ∴Total marks of the class = 40×50 = 2000 Mean marks of the first 20 students = 56 ∴Total marks of the first 20 students = 20×56 = 1120........(1) Mean marks of the last 20 students = 48 ∴Total marks of the last 20 students = 20×48 = 960...........(2) Adding equations (1) and (2), we get Total marks of the first 20 students + total marks of the last 20 students = 1120 + 960 ⇒Total marks of 40 students + marks of the 20thstudent = 2080 ⇒2000 + marks of the 20thstudent = 2080 ∴marks of the 20thstudent = 2080 - 2000 = 80 Like my answer if you find it useful!

23.) The mean marks of a class of 40 students are 50. If the mean of first 20 students are 56 and themean marks of last 20 students are 48, find the marks of the 20th student.

Answer»

Mean marks of 40 students = 50

∴Total marks of the class = 40×50 = 2000

Mean marks of the first 20 students = 56

∴Total marks of the first 20 students = 20×56 = 1120........(1)

Mean marks of the last 20 students = 48

∴Total marks of the last 20 students = 20×48 = 960...........(2)

Adding equations (1) and (2), we get

Total marks of the first 20 students + total marks of the last 20 students = 1120 + 960

⇒Total marks of 40 students + marks of the 20thstudent = 2080

⇒2000 + marks of the 20thstudent = 2080

∴marks of the 20thstudent = 2080 - 2000 = 80

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