解析,
0.78×201
=(0.78)×(200+1)
=0.78×200+0.78
=156.78.

8.5×10.1
=8.5×(10+0.1)
=8.5×10+0.85
=85.85

1.96×0.25-0.25×0.96
=0.25×(1.96-0.96)
=0.25×1
=0.25