a₅=a₁+4d=3+4*2=11
S₂₀=(a₁+a₂₀)/2*20 = (a₁+a₁+19d)*10 = (3+3+19*2)*10 = 44*10 = 440
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a₅=a₁+4d=3+4*2=11
S₂₀=(a₁+a₂₀)/2*20 = (a₁+a₁+19d)*10 = (3+3+19*2)*10 = 44*10 = 440