《2025年考点集训与满分备考四年级数学下册北师大版》

1. 用简便方法计算。
0.99×10.1
 73.4×101 - 73.4
 19.94 + 99.7×99.8
5.5×7.7 + 33×0.55 - 5.5
1.25×32×0.25
 0.125×9.62×80 - 96.2
7.5×2.3 - 0.5×2.5 + 22.5×0.4

答案： 0.99×10.1
=0.99×(10 + 0.1)
=0.99×10 + 0.99×0.1
=9.9 + 0.099
=9.999
73.4×101 - 73.4
=73.4×(101 - 1)
=73.4×100
=7340
1.25×32×0.25
=1.25×8×4×0.25
=(1.25×8)×(4×0.25)
=10×1
=10
0.125×9.62×80 - 96.2
=0.125×80×9.62 - 96.2
=10×9.62 - 96.2
=96.2 - 96.2
=0
19.94 + 99.7×99.8
=99.7×0.2 + 99.7×99.8
=99.7×(0.2 + 99.8)
=99.7×100
=9970
5.5×7.7 + 33×0.55 - 5.5
=5.5×7.7 + 3.3×5.5 - 5.5×1
=5.5×(7.7 + 3.3 - 1)
=5.5×10
=55
7.5×2.3 - 0.5×2.5 + 22.5×0.4
=2.5×3×2.3 - 0.5×2.5 + 2.5×9×0.4
=2.5×6.9 - 0.5×2.5 + 2.5×3.6
=2.5×(6.9 - 0.5 + 3.6)
=2.5×10
=25

2. 用简便方法计算。
2.65×1.7 + 13.5×0.17 9.99×222 + 3.33×333 + 3.33
19.98×37 - 199.8×1.9 + 1.998×20
(1 + 0.12 + 0.23 + 0.34)×(0.12 + 0.23) - (0.12 + 0.23)×(0.12 + 0.23 + 0.34)

答案： 2.65×1.7 + 13.5×0.17
=26.5×0.17 + 13.5×0.17
=(26.5 + 13.5)×0.17
=40×0.17
=6.8
19.98×37 - 199.8×1.9 + 1.998×20
=19.98×37 - 19.98×19 + 19.98×2
=19.98×(37 - 19 + 2)
=19.98×20
=399.6
9.99×222 + 3.33×333 + 3.33
=3.33×3×222 + 3.33×333 + 3.33
=3.33×666 + 3.33×333 + 3.33
=3.33×(666 + 333 + 1)
=3.33×1000
=3330
(1 + 0.12 + 0.23 + 0.34)×(0.12 + 0.23)-(0.12 + 0.23)×(0.12 + 0.23 + 0.34)
=(0.12 + 0.23)×[1 + 0.12 + 0.23 + 0.34-(0.12 + 0.23 + 0.34)]
=(0.12 + 0.23)×[1 + 0.12 + 0.23 + 0.34 - 0.12 - 0.23 - 0.34]
=0.35×1
=0.35