We are not a fan of percentages here. For a novice, they are completely meaningless. Even for an intermediate, they tend not to be useful. Do increasingly heavy sets of five as you warm up until the bar speed starts to slow a little. Then do two more sets there for your first 3x5 workout. Much easier and more useful than worrying about 1 RMs or percentages. Also, buy and read Starting Strength. These topics and many more are covered there in great detail.