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Content
Content
Relationship Between Variables
Linear Relationship
Drawing Straight Lines
Gradient of a Straight line
RelationShip Between Variables
RelationShip Between Variables
Example 1
Let say you get a magical box that works as follows.
If you put 1 sweet in the box, it returns 2 sweets.
If you put 2 sweets in the box, it returns 4 sweets.
If you put x sweets in the box, it returns y sweets.
y = 2(x) = 2x sweets.
Example 2
1 cup of Coffee costs $ 0.80
2 cups of Coffee costs = 2 x 0.80 = $ 1.60
m cups of Coffee costs $c
c = m(0.80) = 0.8m
c = 0.8m
Example 3
A Mobile Phone service provider charges as follows.
Fixed Charge : $10/month
Outgoing Call rates : $0.10/minute
If you do not make any calls at all in a month, you just pay the Fixed Charge $10 for that month
If you make Outgoing calls for 5 minutes in a month, you pay 0.10(50) + 10 = 5 + 10 = $15 for that month
If you make Outgoing calls for k minutes in a month, your payment will be $Y
y = 0.10 k + 10
Linear Relationship
Linear Relationship
Two variables x and y has a linear relationship if y can be expressed as y = mx + c, where m and c are constants.
Drawing Straight Lines
Drawing Straight Lines
Draw the lines : y = 6 – 2x and y = 4x – 6
To draw a straight line, find co-ordinates (x,y) of 3 points.
Mark the co-ordinates in graph paper and connect them with straight lines
Gradient of a Straight Line
Gradient of a Straight Line
Equation of this line is y = 2x, so the gradient is 2.
Vertical Shift = 4 – 2 = 2.
Horizontal shift = 2 – 1 = 1.
Gradient = Vertical shift / horizontal shift = 2/1 = 2.
Straight Line - INteractive
Straight Line - INteractive
Questions
Questions
y = 3x – 5, find the value of y when x = 3
y = 3x – 5, find the value of x when y = 10
Find the gradient of the line: y = 4x + 5
Find the gradient of the line: 2y = – 6x – 8
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