Answer: D
In triangle PQR, PQ = QR = 6 cm [because RS = 6 cm] ∴ ∠PRQ = ∠RPQ Now, ∠PRQ + ∠RPQ = 180° − ∠PQR = 180° − 60° = 120° ∴ ∠PRQ = ∠RPQ = 120° ÷ 2 = 60° ∴ Triangle PQR is an equilateral triangle ∴ PR = 6 cm.
In triangle PQR, PQ = QR = 6 cm [because RS = 6 cm] ∴ ∠PRQ = ∠RPQ Now, ∠PRQ + ∠RPQ = 180° − ∠PQR = 180° − 60° = 120° ∴ ∠PRQ = ∠RPQ = 120° ÷ 2 = 60° ∴ Triangle PQR is an equilateral triangle ∴ PR = 6 cm.