1/15 = 1/25 + 1/80 + 1/100 + 1/2401/25 + 1/100 = 1/201/80 + 1/240 = 1/601/20 + 1/60 = 1/15
四个 60分之一1/60+1/60+1/60+1/60＝1/30+1/30＝1/15
1/58 1/59 1/61 1/62
