For the set (3, 4, 5, 8, x), the mean, the median and the mode all have the same value. What is the value of x?

1 Answer
Apr 1, 2017

5

Explanation:

Since there is only one mode, x must be the mode and be either 3, 4, 5, or 8.

(If x were not one of 3, 4, 5, or 8, then there will be no mode. Since it must be one of 3, 4, 5, or 8, x will be the mode.)

But x cannot be 3 or 8. If it were either 3 or 8, it would not be the median. But the median has the same value as the mode.

Thus, x can only be 4 or 5. Now, if you find the mean of the set when x is 4, you get 3+4+5+8+45=245. If you find the mean of the set when x is 5, you get 3+4+5+8+55=5.