2.5×[

17

28

÷4

1

4

×（0.92-0.88）]×6.3
=2.5×[

17

28

÷

17

4

×0.04]×6.3，
=2.5×[

17

28

×

4

17

×0.04]×6.3，
=2.5×

1

7

×0.04×6.3，
=（2.5×0.04）×（

1

7

×6.3），
=1×0.09，
=0.09．