The cost of the milk per liter is ₹15. Draw the graph for the relation between the quantity and cost. Hence find

(i) the proportionality constant.

(ii) the cost of 3 litres of milk.

(i) k = 15 (ii) ₹45

Let the cost of milk be Y and X be the quantity of milk in liter. As it’s given that cost per one liter is 15rs so increase in quantity will increase the cost of milk. So it’s a direct proportion

Mathematically,

Y = KX

Where K is the constant of proportionality

So we can draw a table

so from the graph it’s clear that y = kx = 15x

Proportionality, k = 15

We can draw a graph using the table given

To find the cost of 3 liter milk we have to draw a line parallel to Y-axis at X = 3 then from the intersection point of that parallel line and the curve draw another line parallel to X-axis so the point of intersection of that line and Y-axis will give the cost of 3 liter of milk.

From the graph its clear that cost of 3 liter is 45 RS.