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1 December, 20:44

The mean of four numbers is 6. Three of them are 3.4,10.7and 7.8. what is the fourth number?

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Answers (2)
  1. 1 December, 21:25
    0
    2.1

    Step-by-step explanation:

    Let x be the 4th number. To find the mean add the 4 numbers and divide by 4

    (3.4 + 10.7+7.8+x) / 4 = 6

    Multiply each side by 4

    (3.4 + 10.7+7.8+x) / 4 * 4 = 6*4

    (3.4 + 10.7+7.8+x) = 24

    Combine like terms

    x+21.9=24

    Subtract 21.9 from each side

    x = 24-21.9

    x = 2.1
  2. 1 December, 21:53
    0
    2.1

    Step-by-step explanation:

    Use the equation

    Sum of elements = average x number of elements

    sum = (6) (4)

    sum = 24

    Add up the numbers we know: 3.4 + 10.7 + 7.8 = 21.9

    24 - 21.9 = 2.1

    This means the fourth number is 2.1
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