For a rhombus, all four sides are equal in length and the diagonals bisect each other at their midpoint.
Since the vertices are given in order P→Q→R→S, the diagonals are PR and QS.
The diagonals must bisect each other, so:
Midpoint of PR = Midpoint of QS
Finding the midpoint of diagonal PR:
P = (8, 5) and R = (0, 5)
Midpoint of PR =(28+0,25+5)
=(4,5)
Finding the midpoint of diagonal QS:
Q = (4, 8) and S = (4, k)
Midpoint of QS =(24+4,28+k)
=(4,28+k)
Setting the midpoints equal:
(4,5)=(4,28+k)
The x-coordinates match. Equating the y-coordinates:
5=28+k
10=8+k
k=2
Therefore, the value of k=2.