Answer:
[tex]0.2\ km\ per\ minute[/tex]
Step-by-step explanation:
[tex]As\ we\ are\ given\ that,\\Time\ Jerry\ takes\ with\ the\ Force\ of\ Wind\ in\ his\ direction=10\ minutes\\Time\ Jerry\ takes\ with\ the\ Force\ of\ Wind\ against\ his\ direction=15\ minutes\\Considering\ only\ the\ direction\ of\ the\ forces\ are\ opposite\ and\ the\\ magnitudes\ equal,\\Let\ the\ time\ Jerry\ take\ travelling\ through\ a\ still\ wind\ be\ x\\Let\ the\ Force\ of\ wind\ be\ F.\\Hence,\\x+F=10\\x+(-F)=15\\By\ simply\ adding\ the\ equations,\\2x=10+15\\2x=25\\x=\frac{25}{2}\\[/tex]
[tex]x=12.5\\Hence,\\Time\ taken\ by\ Jerry\ during\ a\ still\ wind=12.5\ seconds.\\We\ also\ observe\ that\ 12.5\ is\ the\ mean\ of\ 10\ and\ 15\ and\ lies\ between\\ the\ two\ extremes.\\Hence,\\As\ we\ now\ know\ that,\\Distance\ from\ the\ library=2.5\ km\\Time\ taken\ by\ Jerry\ during\ the\ still\ wind=12.5\ minutes\\Hence,\ we\ know\ that\\Speed=\frac{Distance}{Time}\\Here,\\Speed=\frac{2.5}{12.5}\\Speed=\frac{1}{5}\ or\ 0.2\ km\ per\ minute[/tex]
