He can use three bookshelves. there will be 3 math books on each of the three shelves and 2 reading books on each of the shelves. 3 is the greatest common factor of 9 and 6.
Let p be the true proportion of US adults who believe raising the minimum wage will help the economy. A point estimate for p is and a good aproximation (because we have a large sample) for the standard deviation of is . Therefore, a 99% confidence interval for p is given by where and is the th quantile of the standard normal distribution, so we have, , i.e., or equivalently (0.3798, 0.4602).