A student was asked to find the arithmetic mean of the numbers 3, 11, 7, 9, 15, 13, 8, 19, 17, 21, 14 and `x`. He found the mean to be 12. What should be the number in place of `x` ?
Clearly, we have `((3 + 11 + 7 + 9 + 15 + 13 + 8 + 19 + 17 + 21 + 14 + x)/(12))` = 12
or 137 + `x` = 144 or `x` = 144 - 137 = 7.
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