Question

求解一些小数的简便运算题.(1) 7.4*2.3+1.9*2.6+12.6*0.4 (2) 1.25*67.875+12

Answer 1

(1) 7.4*2.3+1.9*2.6+12.6*0.4

=(10-2.6)*2.3+1.9*2.6+(10+2.6)*0.4

=10*2.3-2.6*2.3+2.6*1.9+10*0.4+2.6*0.4

=10*(2.3+0.4)+2.6*(1.9+0.4-2.3)

=27

(2)1.25*67.875+125*6.7875+1250*0.053375

=125*0.67875+125*6.7875+125*0.53375

=125*(0.67875+0.53375+6.7875)

=125*8

=1000