Given=
length of the segment AD is 28 cm
distance between the midpoints of segments AB and CD is 16 cm
find out length of BC
To proof
AD = 28 cm
let the midpoint of the AB is E.
let the midpoint of the CD is F.
E & F are the midpoints i.e these points divide AB & CD in two equal parts.
Let BC = z
Let AE = EB = x ( E is midpoint)
Let CF = FD = y (F is midpoint)
the equation becomes
2x + 2y + z = 28
x + y + z = 16
mulitipy above equation by 2
we get
2x + 2y + 2z = 32
thus solving the equations
2x + 2y + 2z = 32
2x + 2y + z = 28
we get
z = 4 cm
i.e BC = 4 cm
Hence proved