Question

There are 40 students in a class whose average weight is 56.25 kg.Among these 40 students ,25 are boys and 15 are girls. The average weight of 25 boys is 6.8 kg more than the average weight of 15 girls.What is the average weight of 15 girls

Answer 1

Answer:

average weight of 40 students=56.25kg

total weight of 40 students=56.25×40=2250.00kg

let , average weight of 15 girls=x kg

total weight of 15 girls=15x kg

average weight of 25 boys=(x+6.8)kg

total weight of 25 boys=25(x+6.8)kg

ATQ

15x+25(x+6.8)=2250

25x+25x+170.0=2250

40x=2250-170

40x=2080

x=2080/40

=52 kgAns

Answer 2

Average weight of 15 girls is 52 kg.

Step-by-step explanation:

We are given the following in the question:

Number of students in class = 40

Average weight of class = 56.25 kg

Number of boys = 25

Number of girls = 15

Average weight of 25 boys = 6.8 kg

Formula:

$Mean = \displaystyle\frac{\text{Sum of all observations}}{\text{Total number of observation}}$

$\text{Mean of class} = \dfrac{\text{Sum of weight of 40 students}}{40} = 56.25\\\\\text{Sum of weight of 40 students} = 56.25\times 40 = 2250 \text{ kg}$

Let x be the average weight of girls, then we can write

$\text{Mean weight of boys} = \dfrac{\text{Sum of weight of 25 students}}{25} = 6.8+x\\\\\text{Sum of weight of 25 boys} = (6.8+x)\times 25 = (170 + 25x)\text{ kg}$

Sum of weight of 15 girls =

$=\text{Sum of weight of 40 students} - \text{Sum of weight of 25 boys}\\= 2250-(170 +25x)= (2080-25x)\text{ kg}$

Average weight of 15 girls =

$\text{Mean weight of girls} = \dfrac{\text{Sum of weight of 15 girls}}{15} \\\\\Rightarrow \dfrac{2080-25x}{15} = x\\\\\Rightarrow 40x = 2080\\\Rightarrow x = 52$

Thus, average weight of 15 girls is 52 kg.

#Learnmore:

Three maths classes: A, B and C take an algebra test. The average score of class A is 83. The average score of class B is 76. The average score of class C is 85. The average score of class A and B is 79 and average score of class B and C is 81. What is the average score of classes A, B, C ?

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