四分之一加二十八分之一加七十分之一加一百三十分之一加二百零八分之一
=1/3*(1-1/4+1/4-1/7+1/7-1/10+1/10-1/13+1/13-1/16)
=1/3*(1-1/16)
=1/3*15/16
=5/16
这是简便运算,很好用的,希望能帮到你,祝你学习进步,不理解请追问,理解请及时采纳!(*^__^*)
1/4+1/28+1/70+1/130+1/208
=8/28+1/70+1/130+1/208
=2/7+1/70+1/130+1/208
=21/70+1/130+1/208
=3/10+1/130+1/208
=4/13+1/208
=(16*4+1)/208
=65/208
=5/16
=8/28+1/70+1/130+1/208
=4/13+1/208
=5/16