When you want to learn something, performing simple math or reading quickly can help to establish what you have already learned efficiently; this is called brain warming.
Silent reading is known to activate the occipital lobe, temporal lobe, parietal lobe and prefrontal cortex. However, reading aloud is better as it is accompanied by the action of producing sound (voice) and listening to the sound which works a wider range of the brain such as the premotor cortex and the upper temporal gyrus (related to hearing).
The most effective way to warm up the brain is to read aloud as quickly as possible. This method is effective not only for children but also for adults, for example, when trying to study or improve language skills.