Statistics

Ten workers produce the same type of components. Two workers produce one component in $4$ minutes, other three workers in $5$ minutes, another one worker in $6$ minutes, next three workers in $7$ minutes and the last one of them in $8$ minutes. What is the average time needed to produce one component? Round the result to the nearest hundredth.

In a toy-factory four workers make the same toys manually. In one $8$ hour shift the first worker produced $12$ toys, the second $10$ toys, the third $16$ toys and the fourth $12$ toys. What was the average time to produce a toy on that work shift?

Paul drove the first halfway of a test track at a constant speed of $20\mathrm{kph}$ and the second halfway at a constant speed of $30\mathrm{kph}$. We wish to know Paul's average speed. What type of the average do we need to use?

Your stock portfolio had the following returns in the five consecutive years: $10\mathrm{\%}$, $-20\mathrm{\%}$, $0\mathrm{\%}$, $10\mathrm{\%}$, $20\mathrm{\%}$ (the minus sign denotes the financial loss). We are interested in five years compound annual growth rate of the portfolio. What type of average do we need to use?