Often, variability is most usefully expressed in the same units as the original data. That's what <em>standard deviation</em> (square root of variance) does. In situations where that is the case, the variance is useful only for getting to the value of standard deviation.

4 0

2 years ago

The ratio of students in Class X to Class Y is 2 : 5. There are 24 more students in Class Y than Class X. How many students must

Natalka [10]

Answer: 12 students

Step-by-step explanation:

Let X and Y stand for the number of students in each respective class.

We know:

X/Y = 2/5, and

Y = X+24

We want to find the number of students, x, that when transferred from Y to X, will make the classes equal in size. We can express this as:

(Y-x)/(X+x) = 1

---

We can rearrange X/Y = 2/5 to:

X = 2Y/5

The use this value of X in the second equation:

Y = X+24

Y =2Y/5+24

5Y = 2Y + 120

3Y = 120

Y = 40

Since Y = X+24

40 = X + 24

X = 16

Now we want x, the number of students transferring from Class Y to Class X, to be a value such that X = Y:

(Y-x)=(X+x)

(40-x)=(16+x)

24 = 2x

x = 12

12 students must transfer to the more difficult, very early morning, class.

7 0

2 years ago