Math New Drill : Level 2 SNJ00-1003-L2 Two right-angled isosceles triangles in rectangle

Triangle PQR and triangle PRC are right-angled isosceles triangles in rectangle ABCD. 
AP = 5cm and AQ = 3cm. 
Find the length of AD.














Answer
10 cm

Solution
Additional lines are drawn as in the figure below. 


△ APQ and△ EQR are congruent. 
As AP = EQ = 5cm and AQ = ER = 3cm, AE = FR = 3 + 5 = 8 cm and FP = 5 - 3 = 2 cm. 

Next, △ FPR and△ GRC are congruent. 
FP = GR = 2cm and FR = GC = 8cm. 

Therefore AD = FG = 8 +2 = 10 cm.