课后练习第1题答案
(1)C
(2)A
课后练习第2题答案
3.72×99+3.72
=3.72×99+3.72×1
=3.72×(99+1)
=3.72×100
=372 9.98×9.9
=9.98× (10-0.1)
=9.98 ×10-9.98×0.1
=99.8-0.998
=98.802
1.25×0.9×0.8
=1.25 ×0.8×0.9
=1×0.9
=0.9
4×(6.3×2.5)
=(4×2.5)×6.3
=10 × 6.3
=63 6.4×0.25 ×12.5
=(8×12.5)×(0.8×0.25)
=100 × 0.2
=20
2.5 ×16.7-2.5 ×0.7
=2.5×(16.7-0.7)
=2.5×16
=40
课后练习第3题答案
(1)×
1.25×(8+0.8)
=1.25 ×8+1.25 ×0.8
=10+1
=11
(2)×
3.6-1-2.4 × 0.06
=3.6+0.144
=3.744
课后练习第4题答案
(1)5 × 3.6 ×200=3600(元)
(2)(6.2+9.8)×20=320(元)
课后练习第5题答案
(1)2.9 × 0.45+0.29×4.2+0.029 × 13
=2.9 × 0.45 -1-2.9 × 0.42+2.9 × 0.13
=2.9×(0.45+0.42+0.13)
=2.9×1
=2.9
(2)43 ×11.8+5.7×118
=4.3×118+5.7×118
=118×(4.3-1- 5.7)
= 1180