Question

简便运算

① 4.02x1.3+40.2x0.87 ② 0.8x32+3.2x2 ③ 99x12+1.2x10 ④ 87.4x36-3.6x74 ⑤ 8.3x4+0.4x17 好的. 快的可以加分

Answer 1

① 4.02x1.3+40.2x0.87
=4.02 x（1.3 +8.7）
=4.02 x10
=40.2
② 0.8x32+3.2x2
= （0.8+0.2）x32
=1x32
=32
③ 99x12+1.2x10
=（99+1）x12
=100x12
=1200
④ 87.4x36-3.6x74
=3.6x（874-74）
=3.6x800
= 2880
⑤ 8.3x4+0.4x17
=4x（8.3+1.7）
=4x10
=40

这都是运用乘法分配律，关键是要把一个因数变相同

Answer 2

把每一个算式都乘以2
得出1×3+3×5+...+97×99+99×101
也就是3+15+...+9603+9999
你们学过怎样解这个吧!
首项加末项乘以公差(两数间的差,如3与5的差为12,12就是公差)除以二
因为最开始除以了二所以结果要除以二
这下简单了3

Answer 3

① 4.02x1.3+40.2x0.87
=40.2×0.13+40.2×0.87
=40.2×（0.13+0.87）
=40.2×1
=40.2
② 0.8x32+3.2x2
=8×3。2+3.2×2
=3.2×（2+8）
=3.2×10
=32
③ 99x12+1.2x10
=99×12+12×1
=12×（99+1）
=12×100
=1200
④ 87.4x36-3.6x74
=874×3.6-3.6×74
=3.6×（874-74）
=3.6×800
=2880
⑤ 8.3x4+0.4x17
=83×0.4+0.4×17
=0.4×（83+17）
=0.4×100
=40

Answer 4

4.02x1.3+40.2x0.87=4.02x1.3+4.02x10x0.87=4.02x(1.3+8.7)=4.02x10=40.2
0.8x32+3.2x2=0.8x10x3.2+3.2x2=3.2x(8+2)=3.2x10=32
99x12+1.2x10=99x12+12x1=12x(99+1)=12x100=1200
87.4x36-3.6x74=87.4x10x3.6-74x3.6=(874-74)x3.6=800x3.6=2880
8.3x4+0.4x7=8.3x10x0.4=0.4x7=(83+7)x0.4=90x0.4=36

Answer 5

①（4.02x10)x(1.3/10)+40.2x0.87
=40.2x0.13+40.2x0.87
=40.2x(0.13+0.87)
=40.2
② 0.8x32+3.2x2
=（0.8+2/10）x32
=1x32
=32
③ 99x12+1.2x10
=（99+10/10）x12
=100x12
=1200
④ 87.4x36-3.6x74
=3.6x（87.4x10-74）
=3.6x800
= 2880
⑤ 8.3x4+0.4x17
=4x（8.3+17/10）
=4x10
=40