Total surface area of a cuboid of length l, breadth b and height h =2(l×b+b×h+l×h)
Given, total surface area of the cuboid =1216cm2
⇒2(5a×4a+4a×2a+2a×5a)=1216cm2
⇒76a2=1216
⇒a=4
Hence, the length of the cuboid =5a=20 cm, breadth =4a=16 cm, height =2a=8 cm