Finally, it seemed the Hawks had devised a formula for beating Cleveland in the postseason.

Simple, really. Just play perfectly.

Turn the fire hose of 3-point shots against the Cavaliers. Take care of the ball like it was the Hope Diamond. Downsize LeBron James to normal proportions. Play like your margin for error was slimmer than a runway model.

And for three quarters, they did pretty much just that. They could not, however, keep it going for one quarter longer. It was the fourth, the 12 minutes that matter most, the period that Cleveland always seems to own against the Hawks, that it possessed once more in beating the Hawks 121-108.

Leaving the Hawks Paul Millsap to sing the familiar refrain after the 11th loss to the Cavs in 11 all-time postseason games: “Playing (well) for 48 minutes, discipline is a big part of that. The fourth quarter, we didn’t have it.”

“We have to execute better down the stretch,” Hawks coach Mike Budenholzer lamented. Failure to do discover some way to do that in Game Four at Philips Arena Sunday afternoon will spell the end of the season.

James made his first and only 3 of the game to give the Cavs their first lead of second half — 104-103 with 6:23 left — signalling Cleveland’s intention to mount a finishing kick. The Cavs outscored the Hawks 17-4 from there to claim their third double-digit victory in the three games of this series. In the game’s final 6:43, the Hawks managed but two field goals.

And, thus, the Hawks were unable to push the pause button on the Cav-alanche that is threatening to sweep them out of this season, just as a year ago.

Friday, the Hawks made 16 3-point shots — on 47 percent shooting — a franchise playoff record. Point guards Jeff Teague and Dennis Schroder committed but three combined turnovers. Kyle Korver (18 points) found some breathing room. The Cavs simply scored their way out of those complications.

Continuing the 3-point barrage of Game 2, in which they made an NBA-record 25 3’s, the Cavs piled 21 more atop the Hawks Friday. By the time it was done, they had four players with 20-plus points, led by Channing Frye’s 27. Yes, Channing Frye.

Rendered as support players to that bench scorer were the three more noted Cavs. Kyrie Irving and James scored 24 each, and Kevin Love had 21. Leading the Hawks was Al Horford, with 24.

“When the ball is moving, we have some great shooters,” James said. “When we have great shooting, the ball is popping (from player to player) and it has some energy behind it.”

The Hawks Kris Humphries paid the Cavs shooting the ultimate compliment. “It’s up there on a Golden State-type level,” he said.

The Hawks had no answer to the Cavs’ prolific scoring. Not that they didn’t search high and low for one.

The humiliation of the 25-point loss in Game 2 on Wednesday in Cleveland had left Hawks coach Mike Budenholzer in an experimental mood. To start against the Cavs, he trotted out Thabo Sefolosha in the place of Korver, who had been unable to find any sort of launch window against Cleveland (getting off only three 3’s in the first two games). And no more than four minutes into Friday, the Hawks coach called upon a big body largely unused in the postseason, Humphries.

The new look was effective early. The Hawks came out and made their first four shots and sprinted to an early 8-3 lead. Cleveland was only momentarily impressed.

Continuing to flaunt the law of averages, the Cavaliers brought their absurd shooting percentage south. They made six more 3s, in 10 attempts, to take a 31-28 lead at the close of the first quarter.

Ah, but then it was the Hawks’ turn to sample the healing powers of the 3-point shot. And who was it bringing them this gift? None other than the formerly invisible Korver.

The third of his four made 3s of the second quarter gave the Hawks their first lead — 51-50 — since early in the game. From there, the Hawks closed with a 12-5 run to lead by eight at the horn.

The noisiest of Horford’s points came in the first minute of the second half, a thunderous dunk over Love that filled Philips Arena with with the most hopeful energy of this series. It seemed to carry the Hawks through the third quarter.

But then Cleveland awakened.

The Hawks’ last best chance ended when Teague suffered his only turnover of the game. Bringing the ball upcourt, the Hawks down seven with two minutes to play, Teague was ambushed by Irving, who stole the ball from behind. The Cavs went the other way, made one more three (Love), and another night in Atlanta belonged to the Cavaliers.