简算:①1/2+1/3-1/2+1/3 ②4/9+4/9*3/8 ③3/8*6/7*5/12
问题描述:
简算:①1/2+1/3-1/2+1/3 ②4/9+4/9*3/8 ③3/8*6/7*5/12
答
:①1/2+1/3-1/2+1/3=(1/2-1/2)+(1/3+1/3)=0+2/3=2/3
4/9+4/9*3/8 =4/9(1+3/8)=(4/9)*(11/8)=11/18
3/8*6/7*5/12=6/12*3/8*5/7=1/2*3/8*5/7=(3*5)/(2*8*7)=15/112