5.2*99 简便计算 9-7.2-0.8简便计算 37.4*10.1简便计算 2.9-(1.9+0.8)
3个回答

5.2×99

=5.2×(100-1)

=5.2×100-5.2×1

=520-5.2

=514.8

9-7.2-0.8

=9-(7.2+0.8)

=9-8

=1

37.4×10.1

=37.4×(10+0.1)

=37.4×10+37.4×0.1

=374+3.74

=377.74

2.9-(1.9+0.8)

=2.9-1.9-0.8

=1-0.8

=0.2