五年级奥数小数的速算与巧算(一)
1、凑整法简算:
0.125×0.25×0.5×64 1.31×12.5×8×2
1.25×88 1.25×32×0.25
2、拆拼法简算:
1.25×1.08 7.5×9.9 2.5×10.4
3.8×0.99 1991+199.1+19.91+1.991
3、转化法简算:
. ⨯68. +068. 4.6×99+4.6 5.7×9.9+0.1×5.7 99
7.5×101-7.5 9.8+99.8+999.8+9999.8+99999.8 272.4×6.2+2724×0.38
0.999×0.6+0.111×3.6 0.222×0.778+0.444×0.111 0.999×0.7+0.111×3.7
0.888×0.9+0.222×6.4 0.111×5.5+0.555×0.9 1.25×32×2.5
12.5×48 2.5×128×125×5 2.5×56 1.8×5.5
1.25×6.3+37×0.125 7.24×0.1+0.5×72.4+0.049×724
知0.26×4.5=1.17
计算:2.6×4.5=( ) 0.26×45=( ) 0.026×0.45=( )
2.6×0.45=( ) 260×45=( )
4、设数法简算:
(2+3.15+5.87) ×(3.15+5.87+7.32)-(2+3.15+5.87+7.32) ×(3.15+5.87)
(1+0.23+0.34)×(0.23+0.34+0.65)-(1+0.23+0.34+0.65)×(0.23+0.34)
(3.7+4.8+5.9) ×(4.8+5.9+7)-(3.7+4.8+5.9+7) ×(4.8+5.9)
5、数形结合法简算:
1.999×2003-1.998×2004 19.94×2010-19.93×2011
五年级奥数小数的速算与巧算(一)
1、凑整法简算:
0.125×0.25×0.5×64 1.31×12.5×8×2
1.25×88 1.25×32×0.25
2、拆拼法简算:
1.25×1.08 7.5×9.9 2.5×10.4
3.8×0.99 1991+199.1+19.91+1.991
3、转化法简算:
. ⨯68. +068. 4.6×99+4.6 5.7×9.9+0.1×5.7 99
7.5×101-7.5 9.8+99.8+999.8+9999.8+99999.8 272.4×6.2+2724×0.38
0.999×0.6+0.111×3.6 0.222×0.778+0.444×0.111 0.999×0.7+0.111×3.7
0.888×0.9+0.222×6.4 0.111×5.5+0.555×0.9 1.25×32×2.5
12.5×48 2.5×128×125×5 2.5×56 1.8×5.5
1.25×6.3+37×0.125 7.24×0.1+0.5×72.4+0.049×724
知0.26×4.5=1.17
计算:2.6×4.5=( ) 0.26×45=( ) 0.026×0.45=( )
2.6×0.45=( ) 260×45=( )
4、设数法简算:
(2+3.15+5.87) ×(3.15+5.87+7.32)-(2+3.15+5.87+7.32) ×(3.15+5.87)
(1+0.23+0.34)×(0.23+0.34+0.65)-(1+0.23+0.34+0.65)×(0.23+0.34)
(3.7+4.8+5.9) ×(4.8+5.9+7)-(3.7+4.8+5.9+7) ×(4.8+5.9)
5、数形结合法简算:
1.999×2003-1.998×2004 19.94×2010-19.93×2011