计算题 3.4×7.5+34×0.25 3.66×0.8+0.34×0.8-0.8 用五年级的计算方法计算是用梯等式计算

3.4×7.5+34×0.25
=3.4×7.5+3.4×10×0.25
=3.4×7.5+3.4×2.5
=3.4×(7.5+2.5)
=3.4×10
=34
3.66×0.8+0.34×0.8-0.8
=(3.66+0.34-1)×0.8
=3×0.8
=2.4