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PtichkaEL [24]
3 years ago
12

The mean of 12 numbers is 20 and the mean of another 8 numbers is 25 find the mean of the 20 numbers

Mathematics
1 answer:
AysviL [449]3 years ago
8 0

Answer:

22

Step-by-step explanation:

mean is calculated as

mean = \frac{sum}{count}

Given the mean of 12 numbers is 20 , then

\frac{sum}{12} = 20 ( multiply both sides by 12 )

sum = 240

Given the mean of 8 numbers is 25 , then

\frac{sum}{8} = 25 ( multiply both sides by 8 )

sum = 200

Total sum of the 20 numbers = 240 + 200 = 440, then mean of 20 numbers is

mean = \frac{440}{20} = 22

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Answer:

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Step-by-step explanation:

<u>Domain</u>

The domain of a function is the set of x values for which the function is defined. Here, the domain is limited by the values of x that make the square root defined. That is, the expression under the radical cannot be negative:

  -3x +15 ≥ 0

  15 ≥ 3x . . . . . . add 3x

  5 ≥ x . . . . . . . . divide by 3

  x ≤ 5 . . . . . . . . put x on the left (swap sides)

The rest of the notation in the domain expression simply says x is a real number.

  domain: {x ∈ ℝ : x ≤ 5} . . . . . . matches the first choice

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<u>Range</u>

The range of a function is the set of values that f(x) can have. We know the square root can be zero or any positive number. When it is zero, f(x) = -1.

When it is a positive number, that value is multiplied by -4 and added to -1, so f(x) is a number more negative than -1. Then the range of the function is all numbers -1 and below:

  range: {y ∈ ℝ : y ≤ -1} . . . . . . matches the last choice

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<em>Comment on domain/range problems</em>

When working domain and range problems, it works well to have a good understanding of the domain and range limitations of the functions we usually work with: polynomials, square root, logarithm, trig functions, exponential functions. Domain and range problems generally involve combinations of these or ratios of combinations of these.

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