Question

几道有关分数速算巧算的奥数题11、41.2*8.1+11*9—+53.7*1.944 15 15 152、13—+86—

Answer 1

1、41.2*8.1+11*9又1/4+53.7*1.9
=41.2*8.1+11*[9+0.25]+[41.2+12.5]*1.9
=41.2*8.1+41.2*1.9+12.5*1.9+11*9+11*0.25
=41.2*[8.1+1.9]+[10+2.5]*1.9+99+11*0.25
= 412+10*1.9+2.5*1.9+99+1.1*2.5
=412+19+2.5[1.9+1.1]+99
=410+2+20-1+7.5+100-1
=537.5
2、13又4/19+86又15/19*0.25+0.625*86又15/19+86又15/19*0.125
=13又4/19+86又15/19[0.25+0.625+0.125]
=13又4/19+86又15/19*1
=[13+86]+[4/19+15/19]
=99+1
=100