解:(1)[

-

÷(4.9-3.4)]×

=[

-

÷1.5]×

=[

-

÷

]×

=[

-

×

]×

=

×[1-

]×

=

×

×

=

;
(2)6×

+0.75×2
=6×

+

×2
=(6+2)×

=8×

=6;
(3)

×[

+(

-0.25)]
=

×[

+(

-

)]
=

×

=

;
(4)

÷

+

÷

=

×

+

×

=(

+

)×

=1×

=

.
分析:(1)先算小括号内的,再算中括号内的除法,然后算中括号内的减法,最后算括号外的乘法;
(2)把小数化为分数,运用乘法分配律简算;
(3)把小数化为分数,小括号内的结果为0,再算

×

即可;
(4)把除法改为乘法,运用乘法分配律简算.
点评:考查了运算定律与简便运算,四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算律简便计算.