0.425425425...=425/999所以原式=(5+425/999)*0.63=3.418018018018018.....(018的循环)
5.425(425循环）=(5425-5)/999=5420/9990.63=63/1005.425(425循环）*0.63=5420/999*63/100=3794/1110=3.4180(180循环）
