Question

Rob is working on a project to build a model house. Depending on the area of the base, he has to figure out the amount of material he will need. The given graph shows data from his previous attempts.


If he wants to build a house with a base area of 10 square meters, then how much material would Rob need?

• A. $15kg$
• B. $20kg$
• C. $30kg$
• D. $25kg$

Answer 1

The correct option is C $30kg$

First, let’s make a table for the points given on the graph.

$x$	$y$
$1$	$3$
$2$	$6$
$3$	$9$

We can see that there is a line passing through every point on this graph.

It also seems to be passing through the origin $(0,0).$ This means, for this graph, we can have a unit rate $(1,r).$ If we look at our table carefully, the coordinate of this point has been given to us.


Therefore, $r=3$
Now that we know the unit rate, we can find out how much material Rob will need to build a house with a base area of $10sqm.$

Amount of material needed for a house with base area $1sqm=3kg$
Therefore, amount of material needed to build a house with base area $10sqm=(3\times 10)=30kg$