CAMBRIDGE, Mass. (AP) _ An administrator wanted to show the new president of the Massachusetts Institute of Technology the door to his office Monday. But he couldn't find it.

Student pranksters wanted to lay out a welcome for Charles M. Vest, the university's 15th president. They hid the doorway behind a bulletin board with clippings from the student newspaper - the banner headline read ''Vest Takes Over Monday.''

The ''hack'' - as such pranks are known at MIT - was so successful that the administrator thought he was on the wrong floor.

Vest, who arrived just after the confusion had cleared, was undeterred. The bulletin board was moved to a place of honor in the hallway. Vest went to work, toting a bottle of champagne given him by the pranksters.

Vest succeeds Paul E. Gray, who had served since 1980.

He served as provost and vice-president for academic affairs at the University of Michigan for two years. Before that he was dean of the university's College of Engineering for three years.