(3.14 *10+10 * 4) * 2 =142.8 When four pipes are tied together, the iron wire is the least, and the contact between the iron wire and the pipe is only a quarter of that of each pipe, which adds up to the circumference of a pipe. Use 3. The non-contact point is the center distance between two adjacent pipes, the pipe diameter is 10, the center distance is 10, and there is 10*4. Multiply by 2.