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3 years ago

Decrease £28 by 7%? im stuck on my homework

Mathematics

1 answer:

Murljashka [212]3 years ago

5 0

Answer:

£26.04

Step-by-step explanation:

The long way is to figure 7% of £28, then decrease that quantity by the amount you figured.

0.07 × £28 = £1.96

£28 - 1.96 = £26.04

I prefer to realize that the 100% of the value, decreased by 7%, will be 93% of the value. Then only one calculator operation is required.

0.93 × £28 = £26.04

_____

Comment on percent

Some folks get confused by percents. "Percent" essentially means "per hundred". The symbol % is a shorthand way to write /100, which means exactly the same thing. That is, 7% = 7/100 = 0.07. (Similarly, ‰ is a shorthand way to write /1000.)

Comment on percentage increase or decrease

When you're talking about a quantity decreased by some amount, as "£28 decreased by £7", you mean the value £7 is subtracted. When you say "decreased by 7%", the interpretation is different. We don't mean that £28 is decreased by 0.07 (to give £27.93); rather we mean £28 is decreased by 7% of £28. That is 7% of £28 is subtracted from £28.

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According to 2013 report from Population Reference Bureau, the mean travel time to work of workers ages 16 and older who did not

gregori [183]

Answer:

a) 48.80% probability that his travel time to work is less than 30 minutes

b) The mean is 30.7 minutes and the standard deviation is of 3.83 minutes.

c) 13.13% probability that in a random sample of 36 NJ workers commuting to work, the mean travel time to work is above 35 minutes

Step-by-step explanation:

To solve this question, we need to understand the normal probability distribution and the central limit theorem.

Normal probability distribution

Problems of normally distributed samples are solved using the z-score formula.

In a set with mean $\mu$ and standard deviation $\sigma$ , the zscore of a measure X is given by:

$Z = \frac{X - \mu}{\sigma}$

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

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.

In this question, we have that:

$\mu = 30.7, \sigma = 23$

a. If a worker is selected at random, what is the probability that his travel time to work is less than 30 minutes?

This is the pvlaue of Z when X = 30. So

$Z = \frac{X - \mu}{\sigma}$

$Z = \frac{30 - 30.7}{23}$

$Z = -0.03$

$Z = -0.03$ has a pvalue of 0.4880.

48.80% probability that his travel time to work is less than 30 minutes

b. Specify the mean and the standard deviation of the sampling distribution of the sample means, for samples of size 36.

$n = 36$

Applying the Central Limit Theorem, the mean is 30.7 minutes and the standard deviation is $s = \frac{23}{\sqrt{36}} = 3.83$

c. What is the probability that in a random sample of 36 NJ workers commuting to work, the mean travel time to work is above 35 minutes?

This is 1 subtracted by the pvalue of Z when X = 35. So

$Z = \frac{X - \mu}{\sigma}$

By the Central Limit Theorem

$Z = \frac{X - \mu}{s}$

$Z = \frac{35 - 30.7}{3.83}$

$Z = 1.12$

$Z = 1.12$ has a pvalue of 0.8687

1 - 0.8687 = 0.1313

13.13% probability that in a random sample of 36 NJ workers commuting to work, the mean travel time to work is above 35 minutes

8 0

3 years ago

Simplify using the vertical method. (3k + 4)(3k^2 – 5k – 3)

liubo4ka [24]

Answer:

$9k^{3} -3k^{2}-29k-12$

Step-by-step explanation:

Step 1: Expand by distributing sum groups.

$3k(3k^{2} -5k-3)+4(3k^{2} -5k-3)$

Step 2: Expand by distributing terms.

$9k^{3} -15k^{2} -9k+4(3k^{2} -5k-3)$

Step 3: Expand by distributing terms.

$9k^{3}-15k^{2} -9k+12k^{2} -20k-12$

Step 4: Collect like terms.

$9k^{3}+(-15k^{2} +12k^{2} )+(-9k-20k)-12$

Step 5: Simplify.

$9k^{3} -3k^{2}-29k-12$

3 0

3 years ago

The formula Sn =

kobusy [5.1K]

Answer:

I am English read I know math not

6 0

2 years ago

Pls help (4z - 12) - 12z

Pavlova-9 [17]

Answer: the question can only be simplified to -8z-12 because there is no equal sign.

Step-by-step explanation:

(4z - 12) - 12z

-8z-12

4 0

3 years ago

Read 2 more answers

Suppose that $3000 is placed in an account that pays 16% interest compounded each year. Assume that no withdrawals are made from

Papessa [141]

Answer:

a) $3480

b) $4036.8

Step-by-step explanation:

The compound interest formula is given by:

$A(t) = P(1 + \frac{r}{n})^{nt}$

Where A(t) is the amount of money after t years, P is the principal(the initial sum of money), r is the interest rate(as a decimal value), n is the number of times that interest is compounded per year and t is the time in years for which the money is invested or borrowed.

Suppose that $3000 is placed in an account that pays 16% interest compounded each year.

This means, respectively, that $P = 3000, r = 0.16, n = 1$