How do the prisoners in Eliezer's block survive the new year's selection in Night?

The prisoners run about before the selection process,
trying to get some color in their flesh. The more color they have, the more healthy they
will appear. This will ensure that they are chosen for work and not the
crematory.

Also, when the selection process begins, the
prisoners run by Mengele as quickly as possible. They want to appear healthy and they
also are running quickly so Mengele cannot notice their numbers. Remember, the prisoners
are known only by their number. If Mengele does not see their number, he will not be
able to write down their numbers. In this way, the prisoners stand a better chance at
not being selected for the crematory.

In one selection
process, Elie Wiesel lies about his age and he tells the selection committee that he is
a farmer. A farmer has a better chance at being chosen to work. In this way, Elie will
escape the crematory for the time being.