A negative number would not be reasonable in the solution of rate he received on his investment. So we cannot have a negative rate received on the investment if the final amount is more than we started off with.
The reason being, when you have a positive percent rate of a number, you take that percent of the number and add it to the original. For example:
10% interest of $100 would give you $110
Now if that 10% were a -10% then you would be adding a negative number to the original. So:
-10% of 100 would give us $90 because 10% of 100 is 10 then you change it to a -10 and add -10+100=90
So we cannot have a negative rate received on the investment if the final amount is more than we started off with.
the answer is in bold
