Cast a square steel ingot with a side length of 4 decimeters into a rectangular parallelepiped steel with a width of 2 decimeters and a height of 5 decimeters. How long is the steel after casting?
把一块棱长4分米的正方体钢锭铸造成宽2分米，高5分米的长方体钢材，铸造后的钢材有多长？
<result>6.5</result>