(1)248-13×16
=248-208,
=40;
(2)3.9×4.6+3.9×15.4
=(4.6+15.4)×3.9,
=20×3.9,
=78;
(3)
8
9 ×[
7
8 - (
7
16 -
1
8 ) ]
=
8
9 ×[
7
8 -
5
16 ]
=
8
9 ×
9
16 ,
=
1
2 .
(1)248-13×16
=248-208,
=40;
(2)3.9×4.6+3.9×15.4
=(4.6+15.4)×3.9,
=20×3.9,
=78;
(3)
8
9 ×[
7
8 - (
7
16 -
1
8 ) ]
=
8
9 ×[
7
8 -
5
16 ]
=
8
9 ×
9
16 ,
=
1
2 .