DUBAI- Australia and South Africa booked their places in the last four of the ICC U19 Cricket World Cup after winning their respective quarterfinal matches on Sunday. A magnificent century by West Indies' Nicolas Pooran went in vain as Australia reached its third successive semi-final with a comfortable five-wicket victory here, while South Africa's Aiden Markram scored his second consecutive hundred to take his side to an easy nine-wicket win over Afghanistan in Sharjah.Australia and South Africa will clash in the second semifinal of the tournament on February 26, while the first one will be played between England and Pakistan on Monday. Pooram, who came out to bat in the fourth over of the morning with the West Indies tottering at seven for three, was the last batsman out after scoring a scintillating 143 that lifted his side to 208 in 49.5 overs after it had collapsed to 70 for eight at the Dubai International Cricket Stadium. However, the target proved to be a small one for the Australians who achieved the victory in 46.4 overs for the loss of five wickets after openers Matthew Short and Jaron Morgan put on 107 runs for the first wicket. At Sharjah Cricket Stadium, Justin Dill's four-wicket burst helped bowl the Asian side out for 197 and then opener and captain Markram hit an unbeaten 105 to guide his team home in 39.2 overs. Markram hit nine fours in a 118-ball innings and featured in an unbroken 158 runs second wicket stand with Kirwin Christoffels. Earlier, Afghanistan, batting first after making the right call on the spin of the coin, was rocked by Dill and was bowled out for 197. Dill bagged four for 40, his second four-wicket haul of the tournament, while Yaseen Valli took two for 26 and Kagiso Rabada claimed two for 32.