What is the answer to this?

Mathematics

1 answer:

kherson [118]2 years ago

7 0

s = standard version amount

h = high quality version amount

we know that there were 1090 downloads of the song, meaning s + h = 1090.

we also know that the total amount of MBs downloaded was 3353 MBs, and since the standard is 2.1 MBs and the high quality is 4.9MBs, then 2.1s + 4.9h = 3353.

$\begin{cases} s+h=1090\\ 2.1s + 4.9h = 3353\\[-0.5em] \hrulefill\\ h = 1090 - s \end{cases}\qquad \stackrel{\textit{substituting on the 2nd equation}}{2.1s+4.9(1090-s) = 3353} \\\\\\ 2.1s + 5341 - 4.9s = 3353\implies -2.8s + 5341 = 3353 \\\\\\ -2.8s=-1988\implies s = \cfrac{-1988}{-2.8}\implies \boxed{s = 710}$

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Scores on a certain intelligence test for children between ages 13 and 15 years are approximately normally distributed with μ=10

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Given : Scores on a certain intelligence test for children between ages 13 and 15 years are approximately normally distributed with $\mu=106$ and $\sigma=15$ .

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$P(x>92)=1-P(x\leq92)\\\\=1-P(\dfrac{x-\mu}{\sigma}\leq\dfrac{92-106}{15})\\\\=1-P(z\leq })\\\\=1-P(z\leq-0.93)=1-(1-P(z\leq0.93))\ \ [\because\ P(Z\leq -z)=1-P(Z\leq z)]\\\\=P(z\leq0.93)=0.8238\ \ [\text{By using z-value table.}]$