Question

The mean of the data set is 18. What number is missing? 21, 11, __, 27, 22, 13, 16

Explain

Answer 1

16

Explanation:

Sum = mean × n

Sum = 18 × 7 = 126

21 + 11 + x + 27 + 22 + 13 + 16 = 126

x = 16

Answer 2

The unknown number is 16

Explanation:

Let the missing number be x

To find the mean we add up all the numbers and divide by the number of numbers

21, 11, _x_, 27, 22, 13, 16

We know the mean is 18

(21+ 11+x +27+ 22+ 13+ 16)/7 = 18

Multiply each side by 7

(21+ 11+x +27+ 22+ 13+ 16)/7 *7 = 18*7

(21+ 11+x +27+ 22+ 13+ 16) = 126

Combine like terms

110+x = 126

Subtract 110 from each side

110+x-110 = 126-110

x = 16