FIFO/LIFO

In certain questions, it is asked whether ending inventory, COGS, gross profit etc are higher or lower under FIFO and LIFO.
But we know certain things already, i.e., under LIFO, COGS are higher, gross profit is lower et al. So when such a question comes up with values and calculations implied, is it better to just apply the pre-existing concepts or should we be safer and do the calculations?

Just wondering. Though, paranoid me will do the calculations too eitherways.