4.78x14+270.56÷89= 4.78x14+270.56/89【第二项用89约分】=4.78x7x2 +3.04=33.46x2 +3.04=66.92+3.04=69.96
4.78×14+270.56÷89=4.78×10+4.78×4+267÷89+3.56÷89=47.8+5×4-0.22×4+3+0.04=47.8+23-（0.22-0.04）=70.8-0.18=70.62
