Let PS = x cm and PU = k cm Now ST || PR ⇒∠STQ = ∠PRQ = α degree (say) Also, since PQ = PR, ∠PQR = ∠PRQ = α degre Therefore in ∆SQT : ∠SQT = ∠STQ = α degree and hence, SQ = 10- x = ST = k Since PSTU is a parallelogram, PU = ST. Perimeter (PSTU) = 2k + 2x = 2(10 - x) + 2x = 20 cm. Alternate Solution: Take S and T at Q. Perimeter will be 10 + 0 + 10 + 0= 20 cm.