由等差数列的性质可知,Sn,S2n-Sn,S3n-S2n成等差数列,从而可得S10,S20-S10,S30-S20成等差数列即2(S20-S10)=S10+S30-S20,代入可求
【解析】
由等差数列的性质可知,Sn,S2n-Sn,S3n-S2n成等差数列
∴S10,S20-S10,S30-S20成等差数列即2(S20-S10)=S10+S30-S20
∵S10=10,S20-S10=30,
∴60=10+S30-S20
∴S30-S20=50
即a21+a22+…+a30=50
故答案为50