Question

1.a class consists of 50 students out of which 30 are girls . the mean of the maek scored by girls in a test is 73 (out of 100) and that of boys is 71.determine the mean scored of the whole class.

2. mean of 50 observations was found to be 80.4 . but later on ,it was discovered that 96 were misread 69 at one place. find the correct mean.

Answer 1

$\mathbb{ SOLUTION }$ :

1.
Given,
the number of girls out of 50 students = 30

$\therefore$ The number of boys out of 50 students = 50 - 30 = 20

Now,
the marks obtained by 30 girls = 30 × 73 = 2190

and the marks obtained by 20 boys = 20 × 71 = 1420

$\therefore \: mean \: of \: mark \: scored \: by \: girls \: in \: a \: test \: is \: 73 \: and \: that \: of \: boys \: is \: 71$



$\therefore$ Mean score of the whole class

$= \frac{marks \: obtained \: by \: 30 \: girls \: + \: marks \: obtained \: by \: 20 \: girls}{number \: of \: girls \: + \: number \: of \: boys} \\ \\ \\ = \frac{2190 + 1420}{20 + 30} = \frac{3610}{50} = 72.2$



Hence, the mean score of whole class is 72.2.

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2.
Given,
The mean of 50 observations = 80.4

$\therefore$ Sum of 50 observations = 80.4 × 50 = 4020

But later, we observe that 96 was misread as 69 at one place.

Than,
the correct mean

$= \frac{(sum \: of \: 50 \: observation) - 69 + 96}{50} \\ \\ \\ = \frac{4020 - 69 + 96}{50} \\ \\ \\ = 80.94$

Hence, the correct mean is 80.94

Answer 2

Heyy mate ❤✌✌❤

Here's your Answer....

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1.

The mean of 30 girls = 73

The total students = 50

Out of the 30 are girls than the total no. of boys are 50-30 = 20

The score of girls = 73*30 = 2190

The score of boys = 71*20 = 1420

The mean score of whole class = 2190+1420/50

3610/50

361/5

722/10

= 72.2

The mean of whole class = 72.2
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2.

Sum of all 50 observations = mean * no of observation

= 80.4x 50

= 4020

now according to question 96 was misread by 69

So the new sum of observation = 4020 - 69 + 96

= 4020 + 27

= 40.47

now new mean = 4047/50

= 80.94 answer
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