JOHANNESBURG (Reuters) - Half-centuries from Ricky Ponting and Mitchell Johnson helped Australia to secure a 50-run win over West Indies in their Champions Trophy Group A match at the Wanderers on Saturday. Johnson smashed his way to 73 not out off 47 balls with eight fours and three sixes while Ponting scored 79 runs off 95 deliveries as Australia posted 275 for eight in their first match of the tournament. In reply, West Indies could manage only 225 all out in 46.5 overs, with Dale Richards unable to bat due to injury. The defeat was West Indies' second consecutive loss of the tournament, effectively ruling them out of semi-final contention. The left-handed Johnson needed just 40 deliveries to bring up his maiden one-day-international (ODI) 50, eclipsing his previous ODI best of 43 not out scored against England at Lord's earlier this month. In the process, Johnson shared in an eighth-wicket partnership with Brett Lee (25) that realised 70 runs to boost the Australian score after they had stuttered to 171 for seven in the 40th over. So savage was Johnson's assault that 103 runs were scored off the last 10 overs of the Australian innings. Earlier, Ponting strode imperiously to his 69th ODI half-century before he was stumped by Walton off the bowling of left-arm spinner Nikita Miller. Ponting's departure came in the middle of an Australian slump in which the defending champions lost five wickets for 51 runs before Johnson's rescue act. Miller was at the heart of the Australian middle-order collapse as the 27-year-old captured two for 24 off 10 overs. The daunting Australian total proved too much for West Indies despite half-centuries from Andre Fletcher and Travis Dowlin. The duo built an 86-run second-wicket partnership before Fletcher was run out, for 54, by a direct hit from Johnson, fielding at mid-off. Dowlin made his way to a patient 55 off 87 balls before he top-edged a delivery from fast bowler Brett Lee and was caught by wicketkeeper Tim Paine. On Monday, Australia take on India in Centurion while West Indies play their final match, against India, on Wednesday at the Wanderers. SCOREBOARD AUSTRALIA S.Watson b Roach 0 T. Paine c Walton b Bernard 33 R. Ponting st Walton b Miller 79 M. Hussey c Fletcher b Bernard 6 C. Ferguson b Roach 20 C. White b Miller 4 J. Hopes c Walton b Sammy 5 M. Johnson not out 73 B. Lee run out 25 N. Hauritz not out 7 EXTRAS (lb8, w10, nb5) 23 TOTAL (8 wkts, 50 overs) 275 Fall of wickets: 1-0 (Watson), 2-85 (Paine), 3-120 (Hussey), 4-148 (Ponting), 5-162 (White), 6-164 (Ferguson), 7-171 (Hopes), 8-241 (Lee) Did not bat: Peter Siddle BOWLING: Roach 10-0-73-2 (4nb, 4w) Tonge 10-1-54-0 Sammy 10-0-53-1 (2w) Bernard 10-0-63-2 (1nb, 4w) Miller 10-1-24-2 WEST INDIES DS Smith c Paine b Siddle 17 ADS Fletcher run out (Johnson) 54 TM Dowlin c Paine b Lee 55 CAK Walton b Hopes 0 FL Reifer c Hauritz b Watson 28 DE Bernard b Siddle 8 DJG Sammy c Hussey b Watson 20 N Miller c Ponting b Hauritz 4 K Roach c Johnson b Hauritz 3 GC Tonge not out 0 EXTRAS (lb 19, w 16, nb 1) 36 TOTAL (all out; 46.5 overs) 225 Did not bat DM Richards Fall of wickets: 1-38 (Smith, 5.4 ov), 2-124 (Fletcher, 24.3 ov), 3-128 (Walton, 25.2 ov), 4-170 (Dowlin, 36.4 ov), 5-187 (Bernard, 39.1 ov), 6-215 (Sammy, 44.1 ov), 7-219 (Reifer, 44.5 ov), 8-225 (Miller, 46.4 ov), 9-225 (Roach, 46.5 ov) BOWLING B Lee 8-0-41-1 (6w) PM Siddle 8-1-37-2 MG Johnson 10-0-44-0 (4w) SR Watson 7-0-34-2 (1nb) NM Hauritz 7.5-0-23-2 JR Hopes 6-1-27-1 (2w) Toss: West Indies Result: Australia won by 50 runs Man of the match: M Johnson Umpires: Tony Hill (NZL) and Asad Rauf (PAK) TV umpire: Billy Bowden (NZL) Referee: Jeff Crowe (NZL) Reserve umpire: Aleem Dar (PAK).