the mean marks for a french test in a class of 30 boys and 20 girls are 60 and 70 respectively. find the mean mark for the whole class.

Step-by-step explanation:

Let, the number of boys be x and number of girls be y.

\begin{gathered}\\Mean \: marks \: of \: boys \\ = \frac{Total \: marks \: of \: boys }{Total \: number \: of \: boys} \\ \\ 70 = \frac{Total \: marks \: of \: boys}{ x } \\ \\ Total \: marks \: of \: boys = 70x \: \: (1) \\ Mean \: marks \: of \: boys \\ = \frac{Total \: marks \: of \: girls }{Total \: number \: of \: girls} \\ \\ 73 = \frac{Total \: marks \: of \: girls}{y} \\ \\ Total \: marks \: of \: girls = 73y \: \: (2) \\ Mean \: marks \: of \: entire \: students \\ = \frac{Total \: marks \: of \:students}{Total \: number \: of \: students } \\ \\ Mean \: marks \: of \: entire \: students \\ = \frac{Marks \: of \:boys + Marks \: of \: girls}{ Number \: of \: boys + Number \: of \: girls } \\ \\ from \: eq \: (1) \: and \: (2) \\ \\ 71 = \frac{70x + 73y}{x + y} \\ \\ 71(x + y) = 70x + 73y \\ \\ 71x + 71y = 70x + 73y \\ \\ 71x - 70x = 73y - 71y \\ \\ x = 2y \\ \\ \frac{x}{y} = \frac{2}{1} \\ \\ \frac{Number \: of \: boys}{Number \: of \: girls} = \frac{2}{1} \\ \\\end{gathered}

Meanmarksofboys

=

Totalnumberofboys

Totalmarksofboys

70=

x

Totalmarksofboys

Totalmarksofboys=70x(1)

Meanmarksofboys

=

Totalnumberofgirls

Totalmarksofgirls

73=

y

Totalmarksofgirls

Totalmarksofgirls=73y(2)

=

Totalnumberofstudents

Totalmarksofstudents

=

Numberofboys+Numberofgirls

Marksofboys+Marksofgirls

fromeq(1)and(2)

71=

x+y

70x+73y

71(x+y)=70x+73y

71x+71y=70x+73y

71x−70x=73y−71y

x=2y

y

x

=

1

2

Numberofgirls

Numberofboys

=

1

2

answer: your gay

step-by-step explanation:

you dont know math

option: d is the correct answer.

d) none of the above.

step-by-step explanation:

clearly from the figure attached to the question we could see that there is no shape given. hence without any shape given in the figure and after rotation we can't obtained a square pyramid.

since, to obtain a image we need a proper figure of the pre-image so that it can be transformed.

hence, the correct answer is:

d) none of the above.

step-by-step explanation: