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Why do this problem?
This problem offers an introduction to gradients within a
simple environment that allows students to explore all the
important aspects of gradient. This is a suitable preparation for
students to move on to:
Share with the class the definition of gradient given at the
start of the problem. Resist the temptation to give a 'rule' for
working out gradients, as methods should emerge in the discussions
Display a copy of the grid below (a larger version can be
Some of the following questions could be used to get students
thinking about different gradients:
"I'm picturing a line with a gradient of 2 which goes through
H. What other point does it go through?"
"Identify another line with a gradient of 2. How many can you
"Identify a line which is steeper/less steep. Can you find
"Can you find any lines with gradients between 1 and 2?"
"What is the gradient of the line going through G and
"Can you find a steeper/less steep (negative) line? Can you
find another one?"
"Why might it be problematic to work out the gradient of the
line going through R and M?"
Use these questions as an opportunity to share different strategies
for working out the gradients.
Hand out copies of this sheet
students to work in pairs on the main problem:
"How many different gradients can you find? Can you find them
"Arrange them in order of steepness and list the points each line
Expect students to work systematically so that they are in a good
position to justify their findings.
Circulate while students are discussing the problem, and towards
the end of the session invite pairs with interesting approaches to
share their conclusions with the rest of the group.
What does it mean for a line to have positive or negative
What can be said about lines with positive gradients greater
than or less than 1 (or negative gradients greater than or less
A standard method for working out gradients is to divide the
vertical displacement by the horizontal displacement. What is the
connection between this algorithm and the definition of gradient
given at the start of the problem?
Students could move on to
At Right Angles
to consider the gradients of perpendicular
lines, or on to
to investigate the relationship between the
equations of parallel and perpendicular lines on a co-ordinate
Students who are struggling to work systematically could be given
the prompt, explained in the Hint, to fix one end of their ruler at
an extreme point on the grid, and slowly move the other end to
create lines with different gradients.