Atravel agency did a survey and found that the average local family spends $1900 on a summer vacation. the distribution is normally distributed with standard deviation $390. a. what percent of the families took vacations that cost under $1500. round to the nearest percent.

The percentage is 15%

Step-by-step explanation:

* Lets revise how to find the z-score

- The rule the z-score is z = (x - μ)/σ , where

# x is the score

# μ is the mean

# σ is the standard deviation

* Lets solve the problem

- The average local family spends $1900 on a summer vacation

- The distribution is normally distributed with standard deviation $390

- We need to find what percent of the families took vacations that

 cost under $1500

∵ The mean is $ 1900

∴ μ = 1900

∵ The standard deviation is $390

∴ σ = 390

∵ The vacation cost is under $1500

∴ x = 1500

∵ z-score = (x - μ)/σ

- Substitute the values above in the rule

∴ z-score = (1500 - 1900)/390 = -1.0256

- Lets use the normal distribution table of z

∵ P(z < 1500) = 0.1515

∵ P(x < 1500) = P(z < 1500)

∴ P(x < 1500) = 0.1515

∴ The percentage of the families took vacations that cost under

  $1500 is ⇒ 0.15 × 100% = 15%

∴ The percentage is 15%

f

step-by-step explanation:

f

reduce the friction between its moving parts

step-by-step explanation:

in fact, by reducing the friction between the moving parts of the machine, it is possible to reduce the energy wasted due to this friction; therefore, more input energy is converted into useful work, and this will improve the efficiency of the machine.