Learned and learnt are basically the same. They are both used as the past tense form and past participle of "learned". I made a Google search for both the words and the results are: EDU(USA) sites : I learned/learnt 611,000/12,300 I have learned/learnt 162,000/52,100 learned man/learnt man 6530/4 UK sites : I learned/learnt 19,300/13,400 I have learned/learnt 67,800/52,300 learned man/learnt man 4060/3 What the results tell are: American speakers mostly use "learned" for the past and the verbal past participle, while "learned" and "learnt" share roughly equal among British speakers.
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