suppose you have a cache of radium, which has a half-life of approximately 1590 years. how long would you have to wait for 1/4 of it to disappear?

What are the two main ideas of this passage? museum experts feel that museums must change to attract visitors. museum experts care more about the number of visitors than about history. museums that display artworks and exhibits do not make families welcome. museums like colonial williamsburg make learning about the past fun. museums in the united states are different than in other countries.