Simple operation of 12.8 × 0.75 + 2.5 × 1.28
12.8×0.75+2.5×1.28
=1.28×7.5+1.26×2.5
=1.28×(7.5+2.5)
=1.28×10
=12.8
4 × 0.8 × 12.5 × 0.2 simple calculation
4×0.8×12.5×0.2
=4×(0.8×12.5)×0.2
=4×(10×0.2)
=4×2
=8
The topic mainly uses the commutative law of multiplication, and the operation is much more convenient after the commutation
-Simple operation of 4 + (- 12) + 0.5 + 8 + (- 1 / 2)
=-(4+12)+(0.5-1/2)+8
=-16+0+8
=8