1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9
= 3 + 3 + 4 + 5 + 6 + 7 + 8 + 9
= 6 + 4 + 5 + 6 + 7 + 8 + 9
= 10 + 5 + 6 + 7 + 8 + 9
= 15 + 6 + 7 + 8 + 9
= 21 + 7 + 8 + 9
= 28 + 8 + 9
= 36 + 9
= 45
mk tinh nhanh the nay!
=(1+9)+(2+8)+(3+7)+(4+6)+5
=10+10+10+10+5
=40+5
=45
1+2+3+4+5+6+7+8+9=?
=(9+1)+(8+2)+(7+3)+(6+4)+5
=10+10+10+10+5
=10.4+5
=40+5
=45
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9
= 1+9 + 2+8 + 3+7 + 4+6 + 5
=10 + 10 + 10 + 10 +5
= 45 nhé