Answer: Choice B)
We have some value m and we're squaring it to get
To undo this and isolate m, we apply the square root to both sides
There are two solutions here. This is similar to how there are two solutions in something like (those two solutions being x = 5 and x = -5). Squaring any negative number leads to a positive result because
negative times negative = positive.
Solution :
Given data :
The mean length of the steel rod = 29 centimeter (cm)
The standard deviation of a normally distributed lengths of rods = 0.07 centimeter (cm)
a). We are required to find the proportion of rod that have a length of less than 28.9 centimeter (cm).
Therefore, P(x < 28.9) = P(z < (28.9-29) / 0.07)
= P(z < -1.42)
= 0.0778
b). Any rods which is shorter than cm or longer than
cm that re discarded.
Therefore,
P (x < 24.84 or 25.16 < x) = P( -59.42 < z or -54.85)
= 1.052