The sum S of the first n integers is given by the formula S=1/2n(n+1). How many integers must be taken to have a sum of

Mathematics

1 answer:

statuscvo [17]3 years ago

5 0

Answer:

Step-by-step explanation:

We require to solve for n, hence

$\frac{1}{2}$ n(n + 1) = 325

multiply both sides by 2 to eliminate the fraction

n(n + 1) = 650

n² + n = 650

subtract 650 from both sides to have equation in standard form

n² + n - 650 = 0 ← in standard form

(n + 26)(n - 25) = 0 ← in factored form

equate each factor to zero and solve for n

n + 26 = 0 ⇒ n = - 26

n - 25 = 0 ⇒ n = 25

however, n > 0 ⇒ n = 25

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5. Based on recent results, scores on the SAT test are normally distributed with a mean of 1511 and a standard deviation of 312.

Mekhanik [1.2K]

Answer:

The actual SAT score is 2024.

The equivalent ACT score is 29.49.

Step-by-step explanation:

Normal Probability Distribution:

Problems of normal distributions can be solved using the z-score formula.

In a set with mean $\mu$ and standard deviation $\sigma$ , the z-score 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 p-value, we get the probability that the value of the measure is greater than X.

SAT score that is in the 95th percentile

Scores on the SAT test are normally distributed with a mean of 1511 and a standard deviation of 312, which means that $\mu = 1511, \sigma = 312$