用简便方法计算19/20×7%+7/20×81% 4/7×3%+1/7×4%+1/7×12%这是两道题

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用简便方法计算19/20×7%+7/20×81% 4/7×3%+1/7×4%+1/7×12%这是两道题
用简便方法计算19/20×7%+7/20×81% 4/7×3%+1/7×4%+1/7×12%
这是两道题

用简便方法计算19/20×7%+7/20×81% 4/7×3%+1/7×4%+1/7×12%这是两道题
用简便方法计算19/20×7%+7/20×81% 4/7×3%+1/7×4%+1/7×12%
19/20×7%+7/20×81%
=7/20*19%+7/20*81%
=7/20(19%+81%)
=7/20*100%
=7/20
4/7×3%+1/7×4%+1/7×12%
=1/7*12%+1/7*4%+1/7*12%
=1/7(12%+4%+12%)
=1/7*28%
=4%
=0.04