1. An unknown radioactive element decays into non-radioactive substances.In ` 1000` days the radioactivity of a sample decreases by `62` percent. (a)...

1. An unknown radioactive element decays into non-radioactive substances.In ` 1000` days the radioactivity of a sample decreases by `62` percent.

(a) What is the half-life of the element?

(b) How long will it take for a sample of `100` mg to decay to `87` mg?

In what year did/will the exports reach $9.7 billion?