It might be appropriate to include the standard deviation as well as the mean, so you can claim to have given the "best answer" you data allows you to. It is really up to the instructor if you can exclude an outlier to improve your average or standard deviation, if you have the skill, maybe you can perform an ANOVA to determine if an outlier is too far out depending on your confidence level. (I've only heard of people doing an ANOVA, I've never done one myself, so fair warning there.)