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Zolol [24]
3 years ago
7

Two lighthouses flash their lights every 20 and 30 seconds respectively. given that they flash together at 8 p.m., at what time

will they next flash together? answer:
Mathematics
1 answer:
VikaD [51]3 years ago
6 0
Do you remember when you were learning about
Least Common Multiple (LCM) ?  And you were
wondering what on Earth you would ever need it for ?

THIS IS IT !

The amount of time after 8 PM when the lights will flash
together again is the LCM of 20 seconds and 30 seconds.
Do you remember how to find it ?

... When 20 is prime-factored, you have  2 · 2 · 5 .

... When 30 is prime-factored, you have  2 · 3 · 5 .

... So the Least Common Multiple of 20 and 30 is  2 · 2 · 3 · 5  =  60 .

The lighthouses will flash together again in 60 seconds after 8 PM.
That'll be  8:01 PM.  
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Step-by-step explanation:

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18 + -1 = 17

Any other combination of integers that have a product of -18 would have a smaller sum.

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A set of city temperatures in April are normally distributed with a mean of 19.7 degrees Celsius and a standard deviation of 2 d
Sati [7]

Answer:

19.77% of average city temperatures are higher than that of Cairo

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 question, we have that:

\mu = 19.7, \sigma = 2

What percentage of average city temperatures are higher than that of Cairo?

This is 1 subtracted by the pvalue of Z when X = 21.4.

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

Z = \frac{21.4 - 19.7}{2}

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19.77% of average city temperatures are higher than that of Cairo

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