By Bryn PalmerBBC Sport at Millennium Stadium, Cardiff
Wales (3) 27
Tries: Cuthbert, Halfpenny 2
Con: Halfpenny 3
Pen: Halfpenny 2
Scotland (3) 13
Pen: Laidlaw 2
Wales will head to Twickenham in a fortnight with a Six Nations Triple Crown in their sights after a ruthless victory over Scotland in Cardiff.
Three tries in a devastating 14-minute spell early in the second half broke the resistance of the visitors, who went in level at 3-3.
Wing Alex Cuthbert grabbed the first on his home debut, before a brace from Leigh Halfpenny, who converted all three and added a penalty in a 22-point haul.
Scotland, who had Nick de Luca and Rory Lamont sin-binned, broke their try drought via Greig Laidlaw but suffered a fourth straight Test defeat.
Ball possession key to Wales win - Gatland
They battled bravely after the savage blows of Wales' second-half onslaught, but familiar attacking flaws remain unresolved as they prepare to welcome France to Murrayfield next.
Wales captain Sam Warburton was ruled out before kick-off after failing a late fitness test on the dead leg that forced him off in the opening win in Dublin.
Scarlets flanker Aaron Shingler, a Hampshire-born former Glamorgan cricketer whose younger brother Steve is at the centre of an eligibility row between Scotland and Wales, was handed his Test debut.
In a frantic opening, the Scots struggled to get out of their own half but had a chance to score when Wales were penalised at a ruck. However, Laidlaw, starting his first Test at fly-half, pushed his kick wide.
Wales were then penalised for handling in the ruck, allowing Laidlaw to open the scoring.
With half-an-hour gone, Mike Phillips, attempting to clear a ruck, was adjudged to have been impeded by Scotland flanker Alasdair Strokosch, and Halfpenny stroked over the penalty to level it at 3-3.
Missed chances again frustrate Robinson
Scotland, without a try in their last four Tests, had chances to end that barren run before half-time, putting Lee Jones into space down the right flank only for Jonathan Davies to cut the wing down.
But the Scots recycled the ball, through 21 phases, before a knock-on from prop Allan Jacobsen a metre from the Welsh line saw all their efforts come to naught.
That was to prove costly as Chris Cusiter immediately put the visitors on the defensive after the resumption by letting the kick-off drift into touch after failing to control it with his foot.
Ian Evans won the line-out and Wales camped on the Scots' line before going wide, Cuthbert barging through Laidlaw's attempted tackle for his first Wales try.
Official match stats
Minutes in possession
Scrums won (lost)
Line-outs won (lost)
Tackles made (missed)
(delivered by Accenture)
Halfpenny converted and moments later landed a penalty for 10-3 after De Luca was yellow-carded for tackling Davies without the ball as the centre chased his own punt ahead.
The visitors rallied to earn a penalty for Laidlaw to make it 13-6 but Wales duly took advantage of the extra man, showing the composure and cutting edge Scotland lacked.
After sucking in the Scottish defence with a series of charges, the ball was moved wide via Rhys Priestland and James Hook to Cuthbert, who drew the last man and sent Halfpenny over, with the try scorer converting for a 20-6 lead.
Moments later Roberts was freed into space and in the ensuing panic Rory Lamont was yellow-carded for an illegal tackle on Hook, who had replaced the hobbling George North just before the interval.
Scotland, who were also reduced to 13 men in the same fixture two years ago, did well to repel the initial surge after Wales kicked the penalty to touch and won the line-out.
But from an ensuing scrum, Toby Faletau and Phillips combined to put Halfpenny over in the left corner for his second try, and the full-back's conversion from the touchline made it 27-6.
That appeared to spell the end of the match as a contest but the Scots hit back immediately, only to bungle a gilt-edged opportunity when Stuart Hogg, with no-one in front of him, was harshly ruled to have knocked the ball on metres from the Welsh line as he tried to pick up a difficult pass when a more accurate delivery would have left him with a walk-in.
It was a ghastly moment from a Scottish perspective, but minutes later Laidlaw did get over the line, touching down from half a metre out through a forest of bodies. The fly-half's conversion still left the visitors two converted tries behind, but at least it gave them hope.
Hogg then slipped through two tackles as Wales took their foot off the pedal, and a Laidlaw burst and chip ahead was only foiled by quick thinking from Davies.
Wales threatened a fourth try with a minute left after a thrilling break-out led by Priestland, only to concede a penalty for holding on. But a second win of the Championship maintained hopes of a third Grand Slam in eight years.
L Halfpenny; A Cuthbert, J Davies, J Roberts, G North; R Priestland, M Phillips; G Jenkins, H Bennett, A Jones, R Jones (capt), I Evans, D Lydiate, A Shingler, T Faletau.
K Owens (for Bennett, blood, 10-19, 41), P James (for A Jones, 73), L Reed (for R Jones, 75), A Powell (for Lydiate, 73), L Williams (for Phillips, 75), J Hook (for North, 40), S Williams (for Roberts, 78).
R Lamont; L Jones, N De Luca, S Lamont, M Evans; G Laidlaw, C Cusiter; A Jacobsen, R Ford (capt), G Cross, R Gray, J Hamilton, A Strokosch, R Rennie, David Denton.
S Lawson (for Ford, 72), E Kalman (for Cross, 58), A Kellock (for Hamilton, 58) J Barclay (for Strokosch, 44), M Blair (for Cusiter, 48), D Weir, S Hogg (for Evans, 16).
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