(1)4×0.8×2.5×12.5,
=(4×2.5)×(0.8×12.5),
=10×10,
=100;
(2)
3
4 +2
9
17 +
1
4 +3
8
17 ,
=(
3
4 +
1
4 )+(2
9
17 +3
8
17 ),
=1+6,
=7;
(3)6.78×8.5+1.5×6.78,
=(8.5+1.5)×6.78,
=10×6.78,
=67.8;
(4)(
5
12 +
1
9 +
3
8 )×72,
=
5
12 ×72+
1
9 ×72+
3
8 ×72,
=30+8+27,
=65.