Question 981060
The five numbers are of unknown value.  Say u is four of them.
One of them is v.


{{{(4u+v)/5=25}}}


The average of four of them when v is removed becomes 31.


{{{4u/4=31}}}


{{{u=31}}}


-


Now solve for v.
{{{4u+v=5*25}}}
{{{v=5*25-4u}}}
{{{v=125-4*31}}}
{{{v=125-124}}}
{{{highlight(v=1)}}}----------the number which was removed.