Riding on some fine top-order batting, Australia became the third side to enter the ICC Under 19 World Cup Super League semifinals following a comprehensive 119-run win over Pakistan.
They joined England and Afghanistan in the final four on a day when batting first was the order of the day.
The United Arab Emirates set a target beyond hosts West Indies on their way to a Plate semifinal success, while Uganda were 35-run winners in the Plate play-off semifinal against Papua New Guinea.
Half-centuries for Teague Wylie and Corey Miller, as well as a 47 from Campbell Kellaway, helped Australia to 276 for seven from their 50 overs and that proved far too much for Pakistan in Antigua.
Barring a 50-run partnership for the third wicket, Pakistan were always behind in their chase and eventually crumbled to 157 all out with the wickets shared among the Australian bowlers.
Pakistan won the toss and elected to field, but soon regretted that decision as Kellaway and Wylie (71) put on 86 for the first wicket.
Kellaway was stumped off the bowling of Qasim Akram (3-40), but that just brought Miller to the crease and he accelerated the run-rate on his way to 64.
Their stand of 101 was brought to an end by Awais Ali, who had Wylie bowled, with Miller following soon after to leave Australia 203 for three with just under 10 overs remaining.
Skipper Cooper Connolly chipped in with 33 and William Salzmann cracked a quickfire 25 off 14 balls from No.7 to set a competitive target.
It soon became clear that it would be well beyond Pakistan, with Muhammad Shehzad and Haseebullah Khan both caught behind to leave their side 27 for two in the fifth over.
Abdul Faseeh (28) and Irfan Khan (27) started to rebuild before the latter was bowled by Salzmann (3-37), and the wickets fell at regular intervals from then on.
Australia will face the winner of the final Super League quarterfinal between India and defending champions Bangladesh on Saturday.
UAE stun the hosts
A sensational knock from Aayan Afzal Khan helped UAE to one of the greatest results in their history as they beat the West Indies by 82 runs in the Plate semifinals in Trinidad.
After edging past Uganda by a wicket, UAE endured a torrid start when Shiva Shankar (3-31) struck early and often to leave the visitors scrambling at 26 for four.
It was at that point that Aayan entered the fray, and his 93 turned the game on its head. While initially wickets continued to tumble, his 103-run partnership with Shival Bawa (51) for the seventh wicket ensured that the Asian would have something to defend.
He was the last man to fall in a first innings effort of 224 for nine, a target that proved far too much for the Windies.
Jash Giyanani (3-21) made the early inroads, with the home side quickly finding themselves 32 for four. And unlike the UAE, they had no Aayan to save the day, as Dhruv Parashar (4-30) picked up the baton with the ball.
In fact the most resistance from the West Indies came from the final pair, Nathan Edward hitting an unbeaten 51 as he and No.11 Isai Thorne put on 70 for the final wicket before fittingly Aayan sealed the win.
UAE will take on the winner of Ireland against Zimbabwe in the Plate final, while the West Indies take on the loser in the playoff for 11th.
Kakuru fires Uganda past PNG
Cyrus Kakuru inspired Uganda to a 35-run victory over Papua New Guinea in the Plate playoff semi-finals in Trinidad.
His 65 was the foundation of Uganda's 123 all out in a low-scoring affair and Papua New Guinea never really got going in reply, slumping to 88 all out inside 20 overs.
Uganda looked in trouble at 20 for three after electing to bat first, but it was at that point that Kakuru joined his skipper Pascal Murungi.
The captain chipped in with 16, the only other man to make double figures and while John Kariko (5-19) caused chaos, Kakuru motored along to a half-century. He eventually fell caught and bowled to Kariko for 65 off 59 balls with 11 boundaries.
But the reply never really got going, Juma Miyagi (4-29) and Joseph Baguma (3-30) combining to tear through the top order and reduce PNG to 27 for six.
There was no way back from there, despite 26 from Junior Morea as PNG fell well short in reply. Uganda will now take on Scotland in the play-off for 13th.