简便方法计算6年级1/(1*4)+1/(4*7)+1/(7*10)+ +1/(91+94)
问题描述:
简便方法计算6年级1/(1*4)+1/(4*7)+1/(7*10)+ +1/(91+94)
答
1/(1*4)+1/(4*7)+1/(7*10)+ +1/(91*94)=1/3*(1-1/4)+1/3*(1/4-1/7)+1/3*(1/7-1/10)+.1/3*(1/91-1/94)=1/3*(1-1/4+1/4-1/7+1/7-1/10+.+1/91-1/94)=1/3*(1-1/94)=1/3*93/94=31/94