# 2. Choice of problem features

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Novices choose what to do based on surface features of a problem. Experts choose models based on the structural features of a problem.

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In other words, novices view the problem as a set of independent details and they choose one or two of them to focus on, whereas experts see the problem as a single whole.

For example:

(Exam question)

The Golden Gate bridge in San Francisco is a large suspension bridge.

The cable joining the two towers of the bridge (see illustration) can be modeled by the equation:

where y is the height of the cable above the bridge deck in metres and x is the horizontal distance from the left tower in metres.

What is the distance between the towers? (Hint: both towers are the same height. The left-hand tower is at x = 0)

Student solution:

You can see exactly what’s happened. This student saw the quadratic equation and immediately went and found its roots, without looking at the problem in its entirety (and realising that $y\ne 0$!).