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3 years ago

-x+2y=9 -7x-2y=-1 Solve each system by elimination

1 answer:

5 0

X - 2y = - 9
7x + 2y = 1

x - 2y = - 9
(+)
7x + 2y = 1
___________
8x = - 8

x = - 1

- 1 - 2y = - 9
2y = 8
y = 4

i am a mathematics teacher. if anything to ask please pm me

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20 point to the first one who get this right!!

stepan [7]

Answer:

A) 134

15 miles I believe

Step-by-step explanation:

because 71.1 + 55.6 = 126.7- 262.5 = 134.8

4 0

3 years ago

The probability that Billy would pass at least one test is 0.9. The probability that he passes both tests is 0.7. The tests are

allsm [11]

Answer:

0.875

Step-by-step explanation:

Let the probability that Billy passes test 1 be P(A)

Let the probability that Billy passes test 2 be P(B)

P(A n B) = 0.7

P(A) = P(B)

Let them both be numerically x.

P(A) = P(B) = x

P(A') = P(B') = (1 - x)

Probability that he passes at least one test = 0.9

But (probability that he passes at least 1 test) = 1 - (Probabilty that he fails both tests)

Probability that he fails both tests = 1 - 0.9 = 0.1

P(A' n B')= 0.1

P(U) = P(A) - P(A n B) + P(B) - P(A n B) + P(A n B) + P(A' n B') = 1

x - 0.7 + x - 0.7 + 0.7 + 0.1 = 1

2x = 1 + 0.7 - 0.1 = 1.6

x = 0.8

P(A) = P(B) = 0.8

The conditional probability of Billy passing test 2 given the event that he passes test 1 = P(B|A) = P(A n B)/P(A) = (0.7/0.8)

P(B|A) = 0.875

Hope this helps!!!

6 0

3 years ago

Suppose a research firm conducted a survey to determine the mean amount steady smokers spend on cigarettes during a week. A samp

Varvara68 [4.7K]

Answer:

95.44% probability that a sample of 100 steady smokers spend between $19 and $21

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 $s = \frac{\sigma}{\sqrt{n}}$ .