What if you take 20mg adderall xr at 300pm and you take another adderall xr 20mg at 700pm will the two last 24 hours?

That's a lot of Adderall, you'll be up for over 20 hrs. and no doubt get sick

That guy has no idea what he is talking about. If you take the 3 20mg adderal XR at the exact same time, it could last at the very longest 12 hours. Depending on your tolerance, metabolism, if you ate before taking it, if you drank something acidic before taking it. If the food you at was fatty or healthy. If you eat a full meal, the adderall's effectiveness can weaken up to 44%. On an empty stomach you'll get the full effects. If pills were taken at the same time based on all those factors it could last for 4-12 hours. If you spead the 3 pills apart it can last from 12-34 hours.