Answer:
68% of plans cost between $62.16 and $86.52.
Step-by-step explanation:
The Empirical Rule states that, for a normally distributed random variable:
68% of the measures are within 1 standard deviation of the mean.
95% of the measures are within 2 standard deviation of the mean.
99.7% of the measures are within 3 standard deviations of the mean.
In this problem, we have that:
Mean: 74.34
Standard deviation: 12.18
Bell-shaped is the same as normally distributed.
Estimate the number of plans that cost between $62.16 and $86.52.
62.16 is one standard deviation below the mean.
86.52 is one standard deviation above the mean.
By the Empirical rule, 68% of the measures are within 1 standard deviation of the mean.
So
68% of plans cost between $62.16 and $86.52.
each of the sides of your equation
by the value of
on each of your sides
(you get this because we solve the particular equation we added above)
on each of your sides
because it equals to
because it brings us closer and closer to the answer of
by the number
on each of your sides