I need help on knowing how to construct the graph.

Question

Charlie said that Farrah's faucet takes 2.5 minutes to fill a 2 liter bottle with water. Construct a graph to represent this situation.

Answer 1

First, you need to write the equation of a line.  Then we can graph that line.  This is a line because the bottle is being filled at a certain rate.  Ask yourself this question: How many liters can you fill in 1 minute?  To find this out, we divide 2 liters by 2.5 minutes.

 

2 liters / 2.5 minutes = 0.8 liters / minute

 

 

So the rate is 0.8 liters per minute.  This is also the slope of the line.

 

Now we put this in a linear equation.

 

Let x = number of minutes

Let y = number of liters filled

 

 

y = 0.8x

 

y = (8/10)x

 

 

To graph this function, we will plot two points on a coordinate system.  The first point will be the y-intercept.  This point is (0, 0).  Then we plot the second point.  We use this first point as well as the slope to find it.  Go 10 units to the right from the point, and then 8 units up.  This second point is then (10, 8).

 

Finally, connect these two points in a straight line.