Question

1+2+3+4+5+6+7+8+9

Tính nhanh

Answer 1

= (1+9) +(2+8) + (3+7) +(4+6) + 5 = 10 +10 +10 +10 + 5 =45

Answer 2

=45...................................

Answer 3

\(1+2+3+4+5+6+7+8+9\)

\(=\left(1+9\right)+\left(2+8\right)+\left(3+7\right)+\left(4+6\right)+5\)

\(=10+10+10+10+5\)

\(=10\times4+5\)

\(=40+5\)

\(=45\)

Answer 4

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 

= 1 + 9 + 2 + 8 + 3 + 7 + 4 + 6 +5 

= 10 + 10 + 10 + 10 + 5 

= 20 + 20 + 5 

= 40 + 5 

= 45

Answer 5

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 

= (1 + 9) + (2 + 8) + (3 + 7) + (4 + 6) + 5 

= 10 + 10 + 10 + 10 + 5 

= 40 + 5 

= 45

đúng mình nha