How do you use common core (mental math) to find the answer to: 8×25×23=?

1 answer:

5 0

Mental math I'd split it up and simplify it first.

8 × 25 is 4 × 25 two times. So 100 times anything is just the number plus two zeros usually so

8 × 25 × 23
100 × 23
2300 2300 Is the answer

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A college-entrance exam is designed so that scores are normally distributed with a mean of 500 and a standard deviation of 100.

yawa3891 [41]

Answer:

The probability is 0.003

Step-by-step explanation:

We know that the average $\mu$ is:

$\mu=500$

The standard deviation $\sigma$ is:

$\sigma=100$

The Z-score is:

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

We seek to find

$P(x800)$

For P(x>800) The Z-score is:

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

$Z=\frac{800-500}{100}$

$Z=3$

The score of Z = 3 means that 800 is 3 standard deviations from the mean. Then by the rule of the 8 parts of the normal curve, the area that satisfies the conficion of 3 deviations from the mean has percentage of 0.15%

$P(x>800)=0.15\%$

For P(x<200) The Z-score is:

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

$Z=\frac{200-500}{100}$

$Z=-3$

The score of Z = -3 means that 200 is 3 standard deviations from the mean. Then by the rule of the 8 parts of the normal curve, the area that satisfies the conficion of 3 deviations from the mean has percentage of 0.15%

$P(x$