Question

The linear equation representing relation between number of articles (x) and their cost (y) is ____.

• A. y = 30x
• B. x = 30y
• C. 2y = 40x
• D. y = 15x

Answer 1

The correct option is A y = 30x

The table shows that cost of 2 articles is ₹60 and cost of 5 articles is ₹150.

$\because \frac{60}{2}=\frac{150}{5}=30$

$\therefore$ Number of articles and cost are in proportion.

Slope for the above table is:
$m=\frac{\text{Rise}}{\text{Run}}=\frac{150-60}{5-2}=\frac{90}{3}=30$

$\because$ The equation of line representing proportionality relation is y = mx, where m is the slope, the required equation is y = 30x.