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3 years ago

PLEASE I NEED HELP FAST!!!!

Mathematics

2 answers:

zmey [24]3 years ago

6 0

Answer:

5L+13r=F [F stands for flower arrangement(1)]

Step-by-step explanation:

Divide:

30/6=5

5 lilies per flower arrangement

Divide:

78/6=13

13 roses per flower arrangement

Put together:

5L+13r=F

i hope this helps u pls give brainliest and thx ;)

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Find the compound interest for an investment of $3,000 at 7.5% for 4 years. Round to the nearest cent.

Semmy [17]

The nearest cent is going to be %1.00 So it’s B girla

6 0

3 years ago

An investigator compares the durability of two different compounds used in the manufacture of a certain automobile brake lining.

strojnjashka [21]

Answer:

1. The 90% confidence interval for the true difference between average lifetimes for brakes using Compound 1 and brakes using Compound 2 is (-2411.84, -1332.16).

2. The point estimate for the true difference between the population means is of -1872.

Step-by-step explanation:

Before building the confidence interval, we need to understand the central limit theorem and subtraction between normal variables.

Central Limit Theorem

The Central Limit Theorem estabilishes that, for a normally distributed random variable X, with mean $\mu$ and standard deviation $\sigma$ , the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean $\mu$ and standard deviation $s = \frac{\sigma}{\sqrt{n}}$ .

For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.

Subtraction of Normal Variables:

When two normal variables are subtracted, the mean is the subtraction of the means while the standard deviation is the square root of the sum of the variances.

A sample of 212 brakes using Compound 1 yields an average brake life of 47,895 miles. The population standard deviation for Compound 1 is 1590 miles.

This means that $\mu_1 = 47895, \sigma_1 = 1590, n = 212, s_1 = \frac{1590}{\sqrt{212}} = 109.2$

A sample of 180 brakes using Compound 2 yields an average brake life of 49,767 miles. The population standard deviation for Compound 2 is 4152 miles.

This means that $\mu_2 = 49767, \sigma_2 = 4152, n = 180, s_2 = \frac{4152}{\sqrt{180}} = 309.47$

True difference between average lifetimes for brakes using Compound 1 and brakes using Compound 2.

This is the distribution 1 - 2. So

$\mu = \mu_1 - \mu_2 = 47895 - 49767 = -1872$

This is also the point estimate for the true difference between the population means, which is question 2.

$s = \sqrt{s_1^2+s_2^2} = \sqrt{109.2^2+309.47^2} = 328.17$

90% confidence interval

We have that to find our $\alpha$ level, that is the subtraction of 1 by the confidence interval divided by 2. So:

$\alpha = \frac{1 - 0.9}{2} = 0.05$

Now, we have to find z in the Ztable as such z has a pvalue of $1 - \alpha$ .

That is z with a pvalue of $1 - 0.05 = 0.95$ , so Z = 1.645.

Now, find the margin of error M as such

$M = zs = 1.645*328.17 = 539.84$

The lower end of the interval is the sample mean subtracted by M. So it is -1872 - 539.84 = -2411.84

The upper end of the interval is the sample mean added to M. So it is -1872 + 539.84 = -1332.16.

The 90% confidence interval for the true difference between average lifetimes for brakes using Compound 1 and brakes using Compound 2 is (-2411.84, -1332.16).

5 0

4 years ago

Which points are solutions to the system of inequalities shown below check all that apply y>x+1

Arte-miy333 [17]

The points which satisfy the inequalities in discuss are; Choices D (7,10) and F(8,17).

<h3>Which points omg the answer choices satisfy the system of inequalities?</h3>

It follows from the inequality; x > 5.

Also, substituting 5 for x in; y < 2(x); we have;

y < 10.

Hence, the points which satisfy the inequalities are; (8,17) and (7,10).