Đáp án:
1)1+4+7+10+13+16+19+22
= (1+19) + (4+16)+ (7+13) +(10 +22)
=20 + 20 + 20 +32
=92
2) 6 + 8 + 10 + 12 + 14 + 16 + 18
= ( 6+14) + (8+12) +(16+ 18 +10)
= 20+ 20 +44
=84
3) 7 + 10 + 13 + 16 +19 + 22 + 25
= (7 +13 )+ 10 + 16 +19 +22 +25
=112
4) 1 + 5 + 9 + 13 + 17 + 21 + 25 + 29 + 33
= (1+29) + (5+25)+(9+21)+(13+17) +33
=30+30+30 +30 +33
= 153