用简便方法计算下列各题 1.3/4+1/2÷4/5+3/8 2.9/13÷7+1/7×5/13 3.3-3/2×10/21-2/7
问题描述:
用简便方法计算下列各题 1.3/4+1/2÷4/5+3/8 2.9/13÷7+1/7×5/13 3.3-3/2×10/21-2/7
答
1.3/4+1/2÷4/5+3/8
=3/4+1/2*5/4+3/8
=3/4+5/8+3/8
=3/4+(5/8+3/8)
=3/4+1
=7/4
2.9/13÷7+1/7×5/13
=9/13*1/7+1/7×5/13
=1/7*(9/13+5/13)
=1/7*14/13
=2/13
3.3-3/2×10/21-2/7
=3-5/7-2/7
=3-(5/7+2/7)
=3-1
=2