Each test contains forty items. You have a limited time (30 min) to work out the answers, so work as quickly as possible. Don't linger too long over any item; you may be on the wrong track altogether, and might do better with the next one. On the other hand don't  give up too easily; most of the problems can be worked out with a bit of patience. Just use your common sense in judging when to leave an item unsolved. And remember that on the whole items tend to get more difficult later in the test. Everybody should be able to  do some items correctly, but nobody should be able to do all the items  correctly in the time allowed.