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Inessa [10]
3 years ago
12

John is twice as old as Mary. The sum of their ages is 21. How old is Mary?

Mathematics
2 answers:
Mazyrski [523]3 years ago
6 0

Answer:

Mary is 7

Step-by-step explanation:

If their ages combined equals 21 and john is twice Mary’s age then johns age takes up 2/3 of 21. that would b 14. 14 is 2 x 7. and Mary is 7. 14+7=21. Mary is 7 years old

inn [45]3 years ago
4 0

Correct answers are:

J + M = 21

J - 2M = 0

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The ages of armadillos are normally distributed, with a mean of 14 years and a standard deviation of 1.2. Approximately what per
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Answer:

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Step-by-step explanation:

As we know from normal distribution: z(x) = (x - Mu)/SD

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Approach 1 using Standard Normal Distribution Table:

z for x=17: z(17) = (17-14)/1.2 gives us z(17) = 2.5

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Afterwards using Normal Distribution Tables we find the probabilities as under:

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Finally in order to find out the probability between 17 & 13 years we have:

Percentage of armadillos between 13 and 17 years = P(17) - P(13) = 99.379% - 20.327% = 79.052%

The standard normal distribution table is being attached for yours easiness.

Approach 2 using Excel or Google Sheets:

P(17) = norm.dist(17,14,1.2,1)

P(13) = norm.dist(13,14,1.2,1)

Percentage of armadillos between 13 and 17 years = { P(17) - P(13) } * 100

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