@vips and @bunuel:
Since mean and median are the same for evenly spaced sets, so to make the entire set an evenly spaced set x can be made either 0 or 20.
Can this concept be used to find x=10 as the mean and median?
Actually that (such numbers) could be a trap in this question.
You might remember -
If set is evenly spaced then for sure mean=median
But, if mean=median, it doesnt mean that set is evenly spaced. It may or may not be.
So, if we make x=0 and x=20, and find mean and median =10. We are pratically limiting our scope only to evenly spaced sets. And thus we get a few solutions-but not all.
We still need to look for solution for the other case where set is not evenly spaced. (Also x=10 doesnt give u an evenly spaced set.. so concept cant be applied directly, it would be more evident if the number of elements in set is even).
One easy concept that u can use though is, if median =mean then numbers in the set will be symmetrical around median. Why it helps is that finding median is usually very simple,without calculation.
Black Friday Debrief