Why is it that so few of my pupils have a real understanding of performing calculations with negative numbers.
I have recently been working on finding the equation of a line in slope-intercept form with my S3 class. They investigated how to calculate gradient and have a great understanding of how to calculate gradient. The problems arose when actually calculating the gradient. So many errors with calculations such as -4 – (-5).
Listening to conversations at various tables I hear statements like “two negatives make a positive” and “I hate negative numbers”. The main misconceptions seem to be that since 6 – (-3) = 9 then -3 + (-4) = 7 since two negatives make a positive. Continue reading