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OverLord2011 [107]
2 years ago
15

if the sum of a number and seven is doubled, the result is eight less than the number. Find the number

Mathematics
2 answers:
Kipish [7]2 years ago
5 0

Answer:

-22

Step-by-step explanation:

The result is eight less than the number means that

the result = number - 8

( x + 7 ) * 2 = x - 8

=> 2x + 14 = x - 8

=> x = -22

Alexeev081 [22]2 years ago
4 0

Answer: -18

Step-by-step explanation:

Let the number be represented by x.

If the sum of a number and seven is doubled, the result is four less than the number. The expression would be

2(x + 7) = x - 4

We would open the bracket on the left hand side of the equation by multiplying each term inside the bracket by 2. It becomes

2x + 14 = x - 4

Subtracting 14 and x from the left hand side and the right hand side of the equation, it becomes

2x + 14 - 14 - x =x - x - 4 - 14

x = - 18

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The sum of two numbers is <br> 50<br> and the difference is <br> 28<br> . What are the numbers?
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50-28=22

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3 years ago
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The average sunflower has 34 petals. What is the best estimate of the total number of petals on 57 sunflowers?
stellarik [79]
Your initial instinct would be to solve this problem with this solution. 34 x 57 = 1,938 petals.

However, the word estimate is present; therefore, we have to consider that we need to get the approximate number and not the exact number of petals.

There is a general rule regarding estimation or approximation. You have to round it to the nearest place you have based on. In this problem we round it off to the nearest tens place.

If the number is below 5, you round it down: 34 is rounded down to 30 petals.

If the number is above 5, you round it up: 57 is rounded up to 60 sunflowers.

Thus, your equation would be :  30 x 60 = 1,800 petals (best estimate)


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3 years ago
The College Boards, which are administered each year to many thousands of high school students, are scored so as to yield a mean
Marysya12 [62]

Answer:

a) 15.87% of the scores are expected to be greater than 600.

b) 2.28% of the scores are expected to be greater than 700.

c) 30.85% of the scores are expected to be less than 450.

d) 53.28% of the scores are expected to be between 450 and 600.

Step-by-step explanation:

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.

In this problem, we have that:

\mu = 500, \sigma = 100

a. Greater than 600

This is 1 subtracted by the pvalue of Z when X = 600. So

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

Z = \frac{600 - 500}{100}

Z = 1

Z = 1 has a pvalue of 0.8413.

1 - 0.8413 = 0.1587

15.87% of the scores are expected to be greater than 600.

b. Greater than 700

This is 1 subtracted by the pvalue of Z when X = 700. So

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

Z = \frac{700 - 500}{100}

Z = 2

Z = 2 has a pvalue of 0.9772

1 - 0.9772 = 0.0228

2.28% of the scores are expected to be greater than 700.

c. Less than 450

Pvalue of Z when X = 450. So

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

Z = \frac{450 - 500}{100}

Z = -0.5

Z = -0.5 has a pvalue of 0.3085.

30.85% of the scores are expected to be less than 450.

d. Between 450 and 600

pvalue of Z when X = 600 subtracted by the pvalue of Z when X = 450. So

X = 600

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

Z = \frac{600 - 500}{100}

Z = 1

Z = 1 has a pvalue of 0.8413.

X = 450

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

Z = \frac{450 - 500}{100}

Z = -0.5

Z = -0.5 has a pvalue of 0.3085.

0.8413 - 0.3085 = 0.5328

53.28% of the scores are expected to be between 450 and 600.

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lapo4ka [179]

Answer:148

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