Draw ΔPQR in which QR = 5.4 cm, ∠Q = 40° and PR = 6.2 cm.

m∠Q = 30°, m∠P = 60°

m∠Q + m∠P + m∠R = 180° (Angle sum property of triangle)

30° + 60° + m∠R = 180°

90° + m∠R = 180°

m∠R = 180° – 90°

m∠R = 90°