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%

The balanced equation is

4Fe(s) +  3O2(g)  ---> 2Fe2O3(s)

here four moles of Fe will react with O2 to give 2 moles of Fe2O3

mass of Fe reacted = 33.4 grams

moles of Fe reacted = mass of Fe / atomic mass of Fe

moles of Fe reacted = 33.4 / 55.8 = 0.599 moles

moles of Fe2O3 formed = 0.5 X 0.599 = 0.2995 moles

so mass of Fe2O3 formed = moles X molar mass = 0.2995 X 159.69 = 47.83 g