Kiriwera Beazley of Mt Roskill Grammar School asks :-

If humans have brains smarter than computers, why do we use computers?

Garry Tee, a mathematician at the University of Auckland, responded.

A computer can do only what we instruct it to do - but it can operate very quickly and perform immensely lengthy sequences of operations. In particular, computers can readily and accurately perform computations with thousands of millions of arithmetic operations. Even if a human could perform tens of thousands of arithmetic operations, she would get tired, bored and increasingly liable to make mistakes. Computers can be used very effectively to search through huge quantities of data for specified items. Computers are very useful for testing theoretical models by programming them to compute the behaviour of that model, which can be examined and used to refine the model.

However, most computers perform only one operation at a time, and even the largest parallel computers cannot handle very many threads of argument simultaneously. But a human brain has thousands of millions of cells, each of which is connected directly to many other cells, and a large fraction of the cells can be operating simultaneously. Humans can recognize intricate patterns in extremely complicated pictures from a brief glimpse, whereas even the most powerful computer with the best programs for pattern recognition would require much longer time to analyze the picture.