A bag contains 6 red marbles, 6 white marbles, and 4 blue marbles. Find P (red or blue).
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Answer: Choice C
Mean = 37.1
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Explanation:
Refer to the table below. The colum labeled "M" is the midpoint for each age interval. To find the midpoint, add up the endpoints and divide by 2. For example, the midpoint of 18 and 24 is (18+24)/2 = 42/2 = 21. Notice how the values of M are increasing by 7 each time.
The column labeled fM refers to multiplying the frequency f with the midpoint M. Example: fM = 6*21 = 126 in the first row.
Add up everything in the column labeled fM and you should get 1484. Divide this over the sum of the frequencies (40) and the mean is 1484/40 = 37.1
You don't need to use the distributive property because there is nothing to distribute, so all you need to do is combine like terms, and they are like terms because they have the same variable to the same power/exponent which is 1.
To combine fractions (by addition or subtraction), they need to have the same denominator. To do so, you can find the least common multiple of 2 and 4, unless you already know what number 2 and 4 have in common, which is 4.
Multiply
by
to make the denominator = 4
Now combine the like terms