①0.65×6.4-6.5×0.54+65×9%②12.5×0.56+1.4÷25③12+56+1112+1920+2930+4142+5556+7172+8990．

Question

①0.65×6.4-6.5×0.54+65×9%
②12.5×0.56+1.4÷(2)/(5)
③(1)/(2)+(5)/(6)+(11)/(12)+(19)/(20)+(29)/(30)+(41)/(42)+(55)/(56)+(71)/(72)+(89)/(90)．

Answer 1

（1）0.65×6.4-6.5×0.54+65×9%，
=0.65×6.4-0.65×5.4+0.65×9，
=0.65×（6.4-5.4+9），
=0.65×10，
=6.5；
（2）12.5×0.56+1.4÷(2)/(5)，
=7+3.5，
=10.5；
（3）(1)/(2)+(5)/(6)+(11)/(12)+(19)/(20)+(29)/(30)+(41)/(42)+(55)/(56)+(71)/(72)+(89)/(90)，
=(1)/(2)+(1)/(2)+(1)/(3)+(2)/(3)+(1)/(4)+(3)/(4)+(1)/(5)+(4)/(5)+(1)/(6)+(5)/(6)+(1)/(7)+(6)/(7)+(1)/(8)+(7)/(8)+(1)/(9)+(8)/(9)+(1)/(10)，
=1+1+1+1+1+1+1+1+(1)/(10)，
=8(1)/(10)．