In equilateral ΔPQR, S and T are points on the PQ and PR, respectively, such that PS = RT. QT and RS intersect at O. The measure of ∠ROQ is ?

90° 100° 150° 120°

120°

ΔRQT ≅ ΔPRS ∴  PS = RT ∠QRT = ∠SPR = 60° QT = SR ∴ S and T are mid points ∠TQR = ∠QRS = 30° ∠QOR = 180° - 30° - 30°  =  120°