keliling trapesium ABCD =

sisi AB = DC  + EB

EB = √(10² -  8²)
      =√(100 -  64)
      = √36
      = 6 cm

AB = DC + EB = 10 + 6
                        = 16 cm

keliling trapesium = jumlah panjang ke empat sisinya
                             = 8 + 10 + 10 + 16
                             = 44 cm