Question

说一下需要小学六年级上册数学题 四则混合运算及简算题各一道高手都看看吧，谢谢大家6b

Answer 1

1. (1/69+2/71)乘23+25除以71
   =1/69*23+2/71*23+25/71
   =1/3+(46/71+25/71)
   =1/3+1
   =4/3
   
   2.(1+1/2)乘(1-1/2)乘(1+1/3)乘(1-1/3)乘........乘(1+1/9)乘(1-1/9)
   
   =3/2*1/2*4/3*2/3...*10/9*8/9
   
   =1/2*10/9(中间的都约去了)
   
   =5/9
   
   3.1/2乘3+1/3乘4+.......+1/19乘20
   
   =1/2-1/3+1/3-1/4+...+1/19-1/20
   
   =1/2-1/20
   
   =9/20 

2.