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奥数简便运算一,3.6*31又2/5+43.9*6又2/5+6二,(81.4+1/6+1/4+1/5)/(1/6+1/4

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奥数简便运算
一,3.6*31又2/5+43.9*6又2/5+6
二,(81.4+1/6+1/4+1/5)/(1/6+1/4+1/5)
三,51又2/3除以5/3+71又3/4除以7/4+91又4/5除以9/5
四,6又7/10*121+444除以40/99+67*21.2
五,(4又1/19-1/17)*(1/7+1/8+1/9)-4*(1/7-1/8+1/9)+(1/7+1/8+1/9)*(1/17-1/19)
一,3.6*31又2/5+43.9*6又2/5+6
=3.6*(31+2/5)+43.9*(6+2/)+6
=3.6*31+3.6*2/5+43.9*6+43.9*2/5+6
=3.6*30+3.6+(3.6+43.9)*2/5+44.9*6
=108+3.6+47.5*2/5+(45-0.1)*6
=108+3.6+19+270-0.6
=108+19+270+3
=400
二,(81.4+1/6+1/4+1/5)/(1/6+1/4+1/5)
=81.4/(1/6+1/4+1/5) +(1/6+1/4+1/5) /(1/6+1/4+1/5)
=81.4/[(10+15+12)/60]+1
=81.4*60/37+1
=132+1
=133
三,51又2/3除以5/3+71又3/4除以7/4+91又4/5除以9/5
=(50+5/3)/(5/3)+(70+7/4)/(7/4)+(90+9/5)/(9/5)
=30+1+40+1+50+1
=123
四,6又7/10*121+444除以40/99+67*21.2
=6.7*121+6.7*212+444*99/40
=6.7*333+333*3.3
=333*(6.7+3.3)
=3330
五,(4又1/19-1/17)*(1/7+1/8+1/9)-4*(1/7-1/8+1/9)+(1/7+1/8+1/9)*(1/17-1/19)
=(4+1/19-1/17)*(1/7+1/8+1/9)+(1/7+1/8+1/9)*(1/17-1/19)- 4*(1/7-1/8+1/9)
=(1/7+1/8+1/9)(4+1/19-1/17+1/17-1/19)- 4*(1/7-1/8+1/9)
=4*(1/7+1/8+1/9)- 4*(1/7-1/8+1/9)
=4*(1/7+1/8+1/9-1/7+1/8-1/9)
=4*1/4
=1