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I'm new to mathcad prime 3.0. How do I open an older version of mathcad 2001i with mathcad prime 3.0?
You need to have version 15 installed. (You get a copy free with Prime.) There's a conversion script in Prime that uses version 15 to convert the old file. Prime can't read the old file directly, can't convert back (even to a previous version of Prime.)