3.A rectangle with adjacent sides of lengths 5 cm and 4 cm.

Construction:


Step 1: Draw PQ = 5 cm.

Step 2: Draw an angle of \(90^{\circ}\) at Q and cut an arc QR = 4 cm.

Step 3: Draw an arc with centre R and radius 5 cm.

Step 4: Draw another arc with centre P and radius 4 cm to meet the previous arc at S.

Step 5: Join RS and PS.

Hence we have PQRS as the required rectangle.