2. The surface area decreases by 96, indicating that the bottom length 4X4a=96 and a=6 (decimeter). The original height should be 10 decimeter, and the volume is:
6x6xx10 = 360 cubic decimeter.
3. The first time: Divide the 27 ping-pong balls into three groups, with 9 in each group. Two groups were put on the scales. If they are light, they are defective. If they are balanced, the third group is defective.
The second time: divide the 9 defective products into three groups, put the two groups on the balance, the light ones have defective products, and the balance is in the third group.
The third time: put two of the three balls with defective products on the balance. The lighter ball has defective products, and the balance means that the third ball has defective products.
It should be a cube. If so, the volume of steel is 8X8X8=5 12.
Height: 5 12/ 16/8=4 (cm)