Laurie must make 4.5 batches for the school bake sale, and 2 batches for her family. Therefore, in total, Laurie must make 4.5 + 2 = 6.5 batches of cookies.
Since each batch of cookies requires 0.25 pounds of butter, we can multiply that amount by the number of batches baked: 0.25 * 6.5 = 1.625 pounds of butter.
So Laurie uses 1.625 pounds of butter to make all the cookies.