The mystery of the mammoth basketball scores was solved and the Bullets and Maryland Rockets advanced to the final yesterday in the Urban Coalition League's semifinal playoff games at Springarn High School.

Both winners survived in the last minute. The Bullets led by Larry Wright's 49 points, held on to defeat the Maryland Alumni, who were led by John Lucas' 41 points, 200-195.

The Rockets, trailing throughout, got three free throws from Victor Kelly to gain the lead, and held off Adrian Dantley in their 156-155 win over Pappy Parker.

The high scores, seemingly inexplicable when they first occurred in Friday's quarterfinals, turned out to be the result of a defective scoreboard clock.

The problem was in the seconds column. Every time the clock hit nine, it would go blank and then return to nine. Thus, two seconds were added to every 10-second cycle, extending the game nine minutes and 36 seconds beyond its normal 48 minutes.

The major question in the opener was simple could the Maryland Rockets find a way to stop Adrian Dantley?

For three quarters, the former De Matha High All-Met, who earned 1977 rookie-of-the-year honors in the National Basketball Association with the Buffalo Braves, appeared unstopable, withstanding double and triple-teaming, plus the taunting of a great portion of the crowd to score 51 points.

Thanks to Dantley, Pappy Parker led until the Rockets caught them at 153-153 with 55 seconds left in the game.

Dantley then made two free throws to give Pappy the lead again. But on the Rockets' next possession he fouled Victor Kelly. It was Dantley's eighth foul. Kelly was awarded a technical foul shot plus two free throws since all fouls after six call for a technical.

Kelly made all three shots to give the Rockets a 156-155 lead with 27 seconds left, setting the stage for Dantley's last shot.

"We wanted to let Adrian monopolize the ball, said Ollie Johnson, who led the Rockets with 26 points. "Either he was going to have to shoot with three men on him or someone else would have to take the shot. Either way, we didn't want to let him go one-on-one."

Dantley backed in toward the basket and with six seconds left tried a five-foot turnaround jump shot but Johnson slapped it away. Dantley recovered, found three men on him and fed to Rubin Collins. But Collins, who finished with 29 points, had a 20-foot jumper bound away ast the buzzer sounded.

"During the last two minutes they played as a team and that was the difference." Pappy Parker coach Chuck Taylor said, "We wanted to rotate the ball on the last shot and get it to Adrian, but they were playing a zone and we couldn't do it."