六年級數(shù)學(xué)題及答案：分數(shù)的四則混和運算

　　求1/3+1/15 +1/35+ 1/63 +1/99 +1/143

　　簡便方法：

　　1/3=1×(1/3)=1/2(1-1/3)

　　1/15 =(1/3)×(1/5)=1/2(1/3-1/5)

　　1/35=（1/5)×(1/7)=1/2(1/5-1/7)

　　1/63 =(1/7)×(1/9)=1/2(1/7-1/9)

　　1/99 =(1/9)×(1/11)=1/2(1/9-1/11)

　　1/143=(1/11)×(1/13)=1/2(1/11-1/13)

　　所以1/3+1/15 +1/35+ 1/63 +1/99 +1/143

　　=1/2(1-1/3)+1/2(1/3-1/5)+1/2(1/5-1/7)+1/2(1/7-1/9)+1/2(1/9-1/11)+1/2(1/11-1/13)

　　提公因式1/2得1/2(1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13)

　　可觀察到式子中間部分都抵消，最后只剩下1/2(1-1/13)=6/13

　　也就是1/3+1/15 +1/35+ 1/63 +1/99 +1/143=6/13。