In equilateral ΔPQR, S and T are points on the sides PQ and PR respectively, such that PS = TR, QT and SR intersect at Z. The measure of ∠QZR is?

30° 100° 120° 160°

120°

ΔRQT ≅ ΔPRS ∴ SP = TR ∠QRT = ∠SPR = 60° ⇒ QT = SR S and T are midpoints ∠TQR = ∠QRS = 30° ∠QZR = 180° - 30° - 30° = 120°