Question 1058584
The formula that you are looking for is:


FV = PV * (1 + 0.10)^n


where FV is the future value ($10,000), PV is the present value ($200), and n is the number of
trading days.


10,000 = 200(1.10)^n


(1.10)^n = 10000/200


(1.10)^n = 50


Taking the natural logarithm of each side gives you:


n * ln(1.10) = ln(50)


n = ln(50) / ln(1.10)


n = 41.05 trading days


Note: If your calculator does not have the natural logarithm 
function (ln), you can use the regular base-10 logarithm
function (log). As long as you use the same function in both
places, you'll get the same answer.