Question

Franklin saves ₹25 every month. Plot a graph for his savings in 9 consecutive months. Also, find the equation of the line that represents the situation.

Answer 1

Lets try to make a table using the given data.
Starting from month 1, Franklin will have ₹25.
For each consecutive month, ₹25 will be added.

x (Month)	1	2	3	4	5	6	7	8	9
y (₹)	25	50	75	100	125	150	175	200	225

Here we have figured out the x coordinates and y coordinates of the line. Now lets interpret them graphically.

So the graph will be obtained as shown.
Lets take any two points on the line and solve for the slope. The points chosen are (2, 50) and (4, 100).
Now lets find the equation of the line using these two points.
Slope is given by:
$m=\frac{y_2-y_1}{x_2-x_1}$

$m=\frac{100-50}{4-2}$

$m=\frac{50}{2}$

$m=25$

The equation of straight line is, $y-y_1=m(x-x_1)$
Lets take the point (2, 50).

So the equation will be, $y-50=25(x-2)$

$y-50=25(x-2)$
$y=25x-50+50$
$y=25x$