Landry, a 6-foot-7 power forward, and Crump, a 6-1 point guard, combined for 28 of their team's 35 points in the second half as the Boilermakers (4-1) lost most of a 19-point halftime lead before holding on.
Wilson Chandler had 16 points for the Blue Demons (2-4), who made 11 straight shots from the field and drew to 69-63 with 5:06 left on a 3-pointer by Chandler.
Crump put Purdue up 71-63 by converting a drive as the shot clock wound down with 1:51 left. Sammy Mejia hit a 3 with 1:19 left to get DePaul within 71-66, but Landry made two free throws 20 seconds later, the first of 10 straight he and Crump made in the final minute.
Purdue shot 69 percent in taking the 45-26 halftime lead. The Boilermakers hit five straight 3s in a 19-4 run that gave them a 38-17 lead with 6:15 left, and they led by as much as 45-21.
DePaul, which was 2-for-9 on 3s in the opening half, finally started hitting in the second half. The Blue Demons were 18-for-32 over the final 20 minutes, including 5-for-10 from beyond the arc.
David Teague had 14 points and 11 rebounds for Purdue, and Landry, who had 30 points in the consolation semifinal win over Oklahoma, grabbed 10 rebounds.
Draelon Burns added 15 points for DePaul, while Mejia had 13.
Purdue played the second game without starting freshman guard Chris Kramer, who is listed as day to day with a sprained ligament in his right knee.
This was Purdue's second appearance tournament, having lost to North Carolina in the 1999 championship game. This was DePaul's third sixth-place finish in four appearances on Maui. The other was a seventh.
The teams started the trip Saturday on the same flight from Chicago to Maui.