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Suppose you know the mean, but you are missing one of the numbers. ... Now subtract the sum you have from the total sum to find your missing number.
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Suppose you know the mean, but you are missing one of the numbers.
Examples:
85 = mean 86, 83, 81, ___ Find the missing number. You have 4 numbers that have a mean of 85. Multiply 85 ∙4 to get the total sum needed. 85 ∙4 = 340 (total sum) Add the 3 numbers that you know. 86 + 83 + 81 = 250 (sum you have) Now subtract the sum you have from the total sum to find your missing number. 340 250 = 90 (missing number)
73 = mean 75, 94, 32, 75, ___ Find the missing number. Multiply the mean of 73 by 5 (numbers you have). 73 ∙5 = 365 (total sum) Add the numbers you are given. 75 + 94 + 32 + 75 = 276 (sum you have) Subtract the sum you have from the total sum to find your missing number. 365 276 = 89 (missing number)
Practice:
Mean = 37 2) Mean = 90 3) Mean = 40 40, 29, 50, ___ 100, 95, 92, 85, ___ 50, 30, 75, 15, ___
Mean = 75 5) Mean = 50 6) Mean = 81 85, 60, 25, ___ 65, 80, 73, 30, ___ 70, 93, 69, ___
Mean = 25 8) Mean = 31 9) Mean = 100 10, 29, 37, 20, ___ 63, 53, 20, 10, ___ 300, 75, 100, 10, ___
Mean = 130 11) Mean = 70 12) Mean = 91 200, 100, 125, ___ 89, 34, 40, 23, ___ 100, 140, 60, 75, ___
Mean = 39 14) Mean = 48 15) Mean = 88 50, 10, 29, 13, ___ 50, 60, 30, 21, ___ 90, 80, 75, ___
Mean = 45 17) Mean = 80 18) Mean = 20 35, 75, ___ 100, 100, 20, ___ 50, 10, 5, 4, ___
Mean = 35 20) Mean = 70 21) Mean = 35 80, 20, 5, ___ 80, 100, 30, ___ 29, 36, 47, ___
Susan has four 20 point projects for math class. Susan’s scores on the first 3 projects is shown below: Project 1: 18 Project 2: 15 Project 3: 16 Project 4: ?? What does she need to make on Project 4 so that the average for the four projects is 17?