Question

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

Answer 1

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

Answer 2

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

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

= 10 + 10 + 10 + 10 + 5

= 10 x 4 + 5

= 40 + 5

= 45 

Answer 3

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