15pc是多少ly？
15pc = 48.9235ly
是48.9235ly，所以说成49ly也没问题——四舍五入的误差在0.5%以内。
反过来，15ly是多少pc？
15ly = 4.599pc
计算公式: ly = pc × 3.261564
该数值前后的 pc → ly
6 pc19.5694ly
7 pc22.8309ly
8 pc26.0925ly
9 pc29.3541ly
10 pc32.6156ly
11 pc35.8772ly
12 pc39.1388ly
13 pc42.4003ly
14 pc45.6619ly
15 pc48.9235ly
16 pc52.185ly
17 pc55.4466ly
18 pc58.7081ly
19 pc61.9697ly
20 pc65.2313ly
21 pc68.4928ly
22 pc71.7544ly
23 pc75.016ly
24 pc78.2775ly
25 pc81.5391ly