In math class the girl to boy ratio is 8 to 6 if there are 24 girls in the class , how many boys are there ?
1 answer:
Answer: The required number of boys in the class is 18.
Step-by-step explanation: Given that in math class, the girl to boy ratio is 8 to 6 and there are 24 girls in the class.
We are to find the number of boys in the class.
Let 8x and 6x represents the number of girls and boys in the class.
Then, according to the given information, we have
Therefore, the number of boys in the class is given by
Thus, the required number of boys in the class is 18.
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Answer:
The reason why standard deviation of the entire class is greater than standard deviation of males and females considered separately, is that mean values for males and females are different from each other.
Step-by-step explanation:
The concept of mean is well represented by the following formula
mean = , where x1, x2, xn are the observations and N is the number of observations (population).
Standard deviation represents the distance between each observation and the mean of the population (all observations). The formula for this parameter is:
Standard deviation =√[((x1 - x)² + (x2-x)² + ....+ (xn-x)²)/N-1], where x1, x2,..., xn are the observations and x is the mean value.
In this case you have that each height registered is an observation and the number of observations represents the N value. As you can see if the mean for males is different from that of females their standard deviation will be different too. Usually males have heigths greater than that of females (1.77 vs 1.64, in USA for example), and heights inside each group will be more similar than between groups. Then, when you mix all observation there will be an increase in standard deviation, because you are mixing very different heigths