Answer
Percentage increase in productivity: 37.5%
Annual percentage increase: 3.23%
Work Step by Step
The percentage increase in productivity is equal to the change in output over the initial output.
So, in ten years, we have a 1500 bushel increase per worker,
Therefore, the percentage increase in productivity = $\frac{1500}{4000}$ = 37.5%.
The average annual percentage increase in productivity is equal to the tenth root of the above, so when it compounds every year for ten years, it will arrive at the above answer.
If we note by $r$ the annual growth rate:
$(1+r)^{10}=1.375$
$1+r=\sqrt[10]{1.375}$
$r\approx 0.0323=3.23\%$
