Answer:
The standard deviation of car age is 2.17 years.
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 = 7.5
(a) If 99.7% of the ages are between 1 year and 14 years, what is the standard deviation of car age?
This means that 1 is 3 standard deviations below the mean and 14 is 3 standard deviations above the mean.
So

I want to find 



The standard deviation of car age is 2.17 years.
Answer:
Step-by-step explanation:
According to the first expression:
2(10-k): where,
2:shows the double amount of money which ELI has
10:shows the amount of money which ELI had at the starting.
k:shows the amount of money which is lost.
10-k:shows the amount of money which ELI has after losing some amount.
According to the second expression:
20-2k where,
20:shows the twice of initial amount.
k: is the amount of money which is lost
2k:s hows the twice of amount which is lost
20-2k: shows the amount of money which is left with ELI after his mom gave him some money....