Question

18. There are 100 students in a class. The mean height of the class is 150 cm. If the mean height of 60 boys
18,
is 70 cm, find the mean height of the girls in the class.
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Answer 1

Question : There are 100 students in a class. The mean height of the class is 150 cm. If the mean height of 60 boys is 70 cm, find the mean height of the girls in the class ?

Given data : There are 100 students in a class. The mean height of the class is 150 cm and the mean height of 60 boys 18 is 70 cm.

To find : find the mean height of the girls in the class ?

Solution : There are 100 students in class and 60 boys

⟹ Total students = Girls + Boys

⟹ 100 = girls + 60

⟹ Girls = 100 - 60

⟹ Girls = 40

⟹ Mean height of boys = Total height of boys/Total boys

⟹ 70 = Total height of boys/60

⟹ Total height of boys = 70 * 60

⟹ Total height of boys = 4200 cm

⟹ Total height = Total Girls height + Total Boys height

Let, height of girls be x

⟹ Total height = x + 4200

⟹ Mean height = Total height/Total students

⟹ 150 = x + 4200/100

⟹ 150 * 100 = x + 4200

⟹ 15000 = x + 4200

⟹ x = 15000 - 4200

⟹ x = 10800 cm

Now,

⟹ Mean height of girls = Total height of girls//Total girls

⟹ Mean height of girls = 10800/40

⟹ Mean height of girls = 270 cm

Answer : Mean height of girls in class is 270 cm.

Answer 2

Step-by-step explanation:

Given : There are 100 students in class. The mean height of the class is 150cm and the mean height of 60 boys 18 is 70cm

Find :We have to find the mean height of the girls in the class?

Solution :There are 100 students in class and 60 boys

➩ Total students = girls + boys

➩ 100 = girls + 60

➩ girls = 100 - 60

➩ girls = 40

$Mean \: height \: of \: the \: boys = \: \: \: \: \\ \frac{Total \: height \: of boys}{Total \: boys}$

$⟹70 = \frac{Total \: height \: of \: boys}{60}$

$⟹Total \: height \: of \: boys = 70 \times 60$

$Total \: height \: of \: boys = 4200cm$

⟹Total height = Total girls height + Total boys height

Let, height of girls be X

⟹ Total height = X + 4200

$Mean \: height = \frac{Total \: height}{Total \: student \: }$

$⟹150 = x + \frac{4200}{100}$

$⟹150 \times 100 = x + 4200$

$⟹15000 = x + 4200$

$⟹x = 15000 - 4200$

$⟹x = 10800cm$

$Now, mean \: height \: of \: the = \frac{Total \: height \: of \: girls}{Total \: girls}$

$Mean \: height \: of \: girls = \frac{10800}{40}$

$Mean \: height \: of \: girls = 270cm$

Mean height of the girls in class is 270cm