简便运算6.8×16.8+19.3×3.281.5×15.8+81.5×51.8+67.6×18.5235×12.1+235×42.2-135×54.31234+2341+3412+41231/7×3/4+3/7×1/6+6/7×1/12

Question

简便运算
6.8×16.8+19.3×3.2
81.5×15.8+81.5×51.8+67.6×18.5
235×12.1+235×42.2-135×54.3
1234+2341+3412+4123
1/7×3/4+3/7×1/6+6/7×1/12

Answer 1

6.8×16.8+19.3×3.2

=6.8x16.8+（16.8+2.5）x3.2

=16.8x（6.8+3.2）+2.5x3.2

=168+5x0.5x0.4x8

=168+2x4

=176

81.5×15.8+81.5×51.8+67.6×18.5

=81.5×（15.8+51.8）+67.6×18.5
=81.5×67.6+67.6×18.5
=67.6×（81.5+18.5）
=67.6×100
=6760

235×12.1+235×42.2-135×54.3

=235×（12.1+42.2）-135×54.3
=235×54.3-135×54.3
=（235-135）×54.3
=100×54.3
=5430

1234+2341+3412+4123
通过观察,每一位上都有1,2,3,4
于是

1234+2341+3412+4123
=（1+2+3+4）×1111
=10×1111
=11110

1/7×3/4+3/7×1/6+6/7×1/12

=1/7×3/4+1/7×3/6+1/7×6/12
=1/7×(3/4+3/6+6/12)
=1/7×7/4
=1/4