In the given figure, AB = CD and BE = FD.

By which congruency criterion is ΔABF congruent to ΔCDE?

It is given that BE = FD

Adding EF on both sides, we get

BE + EF = FD + EF

⇒ BF = DE   ...(i)

In ΔABF and ΔCDE,

AB = CD   [Given]

∠ABF = ∠CDE = 90^o

BF = DE   [From (i)]

∴ ΔABF ≅ ΔCDE   [By SAS congruency criterion]

So, AF = CE   [By CPCT]

Thus, ΔABF is congruent to ΔCDE by SAS congruency criterion.