Question

Tính nhanh : 

1/10 + 2/9 +3/8 + 4/7 + 5/6 + 1/6 + 3/7 + 5/8 + 7/9 + 9/10

Answer 1

1/10+2/9+3/8+4/7+5/6+1/6+3/7+5/8+7/9+9/10

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

=1+1+1+1+1

=5

Answer 2

1/10 + 2/9 + 3/8 + 4/7 + 5/6 + 1/6 + 3/7 + 5/8 + 7/9 + 9/10

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

= 10/10 + 9/9 +8/8 +7/7 +6/6

= 1 + 1 + 1 + 1 + 1

= 5 .

Answer 3

1/10 + 2/9 +3/8 + 4/7 + 5/6 + 1/6 + 3/7 + 5/8 + 7/9 + 9/10=5