Question on Genectics?

Okay, this is a question that was given to me in biology and I have answered it. I just want to know if my answer's right, and if not, why my answer is wrong:

In a monohybrid cross involving dominance, two red flowers (Rr) are crossed producing 160 offspring. Of the offspring, 115 are red (RR and Rr) and 45 are white (rr). Determine the expected results and calculate the perent deviation. The experimental hypothese is that red color is dominant to white and that both parents are hybrid for red color. Based on your work, do you feel the actual results are close enough to the expected to make the experimental hypothesis acceptable?

So I did the punnet square and got:

RR | Rr

-----------

Rr | Rr

Then I said that the expected results for red were 120 and for white: 40. B/c 3/4 of the punnet square were dominant for red and only 1/4 of the number was white. Then I calculated that the percent deviation was 6.25. And I think, based on my work, the actual results were close enough to the expected that the hypothesis was yes, acceptable.