What this exercise trains
Simple arithmetic appears one problem at a time, and you pick the answer before the timer empties. Correct answers extend the run and raise the difficulty; a wrong one ends it.
The skill here is processing speed — how quickly you carry out easy operations under time pressure. It is one of the four indices in modern IQ batteries, and the one most affected by practice, fatigue and caffeine, which is worth remembering before reading much into a single run.
Training exercises are not a scored assessment. For a measured result across four reasoning domains, take the free IQ test, and see our methodology for how that score is worked out. More exercises are on the training page.