Question

3.2x2.1+3.4×4.2简便方法？

Answer 1

解:该题中，用简便方法计算，可将4.2化成2.1Ⅹ2，再提取题目中
两个相同的小数2.1，则剩下的小数的和正好是10，具体过程如下:
3.2X2.1十3.4Ⅹ4.2
=3.2X2.1十3.4X2.1X2
=2.1X(3.2十6.8)
=2.1X10
=21

Answer 2

3.2x2.1+3.4×4.2
=3.2x2.1+3.4×2.1x2
=3.2x2.1+6.8x2.1
=(3.2+6.8)x2.1
=10x2.1
=21
所以，3.2x2.1+3.4×4.2=21

Answer 3

因为4.2＝2×2.1，所以原算式可以化为：3.2×2.1+3.4×2×2.1＝3.2×2.1+6.8×2.1＝（3.2+6.8）×2.1＝10×2.1＝21

Answer 4

3.2×2.1+3.4×4.2
=3.2×2.1+6.8×2.1
=2.1×(3.2+6.8)
=2.1×10
=21.

Answer 5

3.2x2.1+3.4x4.2
=1.6x4.2+3.4x4.2
=4.2x(1.6+3.4)
=4.2x5
=21

追答

3.2x2.1+3.4x4.2
=1.6x4.2+3.4x4.2
=4.2x(1.6+3.4)
=4.2x5
=21