五分之四乘四加五分之二乘二加五分之一乘十六等于五分之四乘四加五分之四加五分之四乘四等于四加一加四括号乘五分之四等于五分之三十六
五分之四乘四加五分之二乘二加五分之一乘十六 =0.8×(4+1+4)=0.8×9=7.2
4/5*4+2/5*2+1/5*16=1/5*16+1/5*4+1/5*16=1/5*(16+4+16)=36/5