Question

1+3+5+7+9+11+13+15+17+19

Answer 1

1+3+5+7+9+11+13+15+17+19

=(1+19)+(3+17)+(5+15)+(7+13)+(9+11)

=20+20+20+20+20

=20x5

=100

Answer 2

19+1  +   17+3    +    15+5    +     13+7    +    11+9=20 nhan 5 =100. nhé

Answer 3

1+3+5+7+...+19= ( 1 +19) + (2+18) = (3+17) +....+ (9+11)

=20+20+20+20+20

=100

Answer 4

1+3+5+7+9+11+13+15+17+19

= (1+19)+(3+17)+(5+15)+(7+13)+(9+11)

= 20+20+20+20+20

=20 x 5

= 100