( 10+90)+(20+80)+(30+70)+(40+60)+50
= 100+100+100+100+50
=100*4+50
=400+50
=450
tính nhanh
10+20+30+40+50+60+70+80+90=450
tk mk nha
##tohka_yatogami
10 + 20 + 30 + 40 + 50 + 60 + 70 + 80 + 90
= ( 10 + 90 ) + ( 20 + 80 ) + ( 30 + 70 ) + ( 40 + 60 ) + 50
= 100 + 100 + 100 +100 + 50
= 450
10+20+30+40+50+60+70+80+90
=(10+90)+(20+80)+(30+70)+(40+60)+50
= 100 + 100 + 100 + 100 +50
= 450
Ai k mình mình k lại 3 cái luôn
