The mean of the marks secured by 25 students of section A of class X i

1.	The mean of the marks secured by 25 students of section A of class X is 47, that of 35 students of section B is 51 and that of 30 students of section C is 53. Find the combined mean of the marks of students of three section of class X.
Answer» Mean of the marks of 25 students of XA = 47 ∴Sum of the marks of 25 students = 25 × 47 = 1175 ......(i) Mean of the marks of 35 students of XB = 51 ∴Sum of the marks of 35 students = 35 × 51 = 1785 ........(ii) Mean of the marks of 30 students of XC = 53 Sum of the marks of 30 students = 30 × 53 = 1590.........(iii) Adding (i), (ii) and (iii) Sum of the marks of (25 + 35 + 30) i.e., 90 students = 1175 + 1785 + 1590 = 4550 Thus the combined mean of the marks of students of three sections = 4550/90 = 50.56

The mean of the marks secured by 25 students of section A of class X is 47, that of 35 students of section B is 51 and that of 30 students of section C is 53. Find the combined mean of the marks of students of three section of class X.

Answer»

Mean of the marks of 25 students of XA = 47

∴Sum of the marks of 25 students = 25 × 47 = 1175 ......(i)

Mean of the marks of 35 students of XB = 51

∴Sum of the marks of 35 students = 35 × 51 = 1785 ........(ii)

Mean of the marks of 30 students of XC = 53

Sum of the marks of 30 students = 30 × 53 = 1590.........(iii)

Adding (i), (ii) and (iii)

Sum of the marks of (25 + 35 + 30) i.e., 90 students

= 1175 + 1785 + 1590 = 4550

Thus the combined mean of the marks of students of three sections

= 4550/90 = 50.56

Discussion

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