Question

The mean of the marks secured by 25 students of section A of class 10 is 47, that of 35 students of section B is 51 and that of 30 students of section C is 53. find the mean of the marks of the students of three sections of class 10.​

Answer 1

$\pink{\large \mathfrak \blue {solution \: \: : - } }$

$\small \ 1.\: Mean \: of \: the \: marks \: \\ \small of \: 25 \: students \: of \: \\ \small XA = 47$

∴ Sum of the marks of 25 students = 25 × 47 = 1175 ----(¡)

$\small \: 2.Mean \: of \: the \: marks \: \\ \small of \: 35 \: students \: of \: \\ \small XB = 51$

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

$\small \:3. Mean \: of \: the \: marks \: \\ \small \: of \: 30 \: students \: of \: \\ \small XC = 53$

∴ Sum of the marks of 30 students = 30 × 53 = 1590 --- (¡¡¡)

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

Sum of the marks of (25 + 35 + 30)

$\small1175 + 1785 + 1590 = 4550$

$\huge \: = \frac {4550} {9}$

$\huge = 50.56$