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# Electric Kettle

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### Intersections

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Age 14 to 16

Challenge Level

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It is not envisaged that this problem would be used as a class problem. It is more appropriate for an enthusiastic student or small group of students looking for a challenge to work on independently.

Change one equation in this pair of simultaneous equations very slightly and there is a big change in the solution. Why?

Position the lines so that they are perpendicular to each other. What can you say about the equations of perpendicular lines?