Question

13.6×7.9-2.8×7.9+10.8巧算 2.8×9.2+28×0.07巧算

Answer 1

解：
13.6×7.9-2.8×7.9+10.8

=7.9x(13.6-2.8)+10.8
=7.9x10.8+10.8
=10.8x(7.9+1)
=10.8x8.9
=10.8x(9-0.1)
=10.8x9-10.8x0.1
=96.12
2.8×9.2+28×0.07
=2.8x(9.2+0.7)
=2.8x9.9
=2.8x(10-0.1)
=28-0.28
=27.72

Answer 2

13.6×7.9-2.8×7.9+10.8
=7.9x(13.6-2.8)+10.8
=7.9x10.8+10.8
=10.8x(7.9+1)
=10.8x8.9
=10.8x(9-0.1)
=97.2-1.08
=96.12
2.8×9.2+28×0.07

=2.8x9.2+2.8x0.7
=2.8x(9.2+0.7)
=2.8x(10-0.1)
=2.8x10-2.8x0.1
=28-0.28
=27.72

Answer 3

（1）13.6×7.9-2.8×7.9+10.8=7.9×（13.6-2.8）+10.8=10.8×7.9+10.8=10.8×8=86.4
（2）2.8×9.2+28×0.07=2.8×9.2+2.8×0.7=2.8×9.9=2.8×10-2.8×0.1=27.72

Answer 4

13.6×7.9-2.8×7.9+10.8=(13.6-2.8)×7.9+10.8=10.8×7.9+10.8×1=10.8×(7.9+1)=10.8×8=86.4
2.8×9.2+28×0.07=2.8×9.2+2.8×0.7=2.8×(9.2+0.7)=2.8×9.9=2.8×(10-0.1)=28-2.8=25.2