I don't think scholarships stack, unless they are partial and do not cover full tuition fees/living expenses. I guess the intention of these scholarships is to help as many deserving students as possible, doesn't make sense if a few students get multiple awards and the rest get none. I remember Gates has a clause that says they will reduce the stipend proportionately if a candidate is receiving funding from another source. I pulled out of the process for 2 other scholarships too, the moment i found out i got Gates.