The list price of a bicycle is ₹ 4,000. It is sold at a discount of 18%. If GST is 18%, find the selling price including GST.

The list price of a bicycle = ₹ 4,000

Discount = 18% of ₹ 4,000

$\Rightarrow\dfrac{18}{100} \times ₹ 4,000\\[1em] \Rightarrow\dfrac{9}{50} \times ₹ 4,000\\[1em] \Rightarrow ₹ \dfrac{36,000}{50}\\[1em] \Rightarrow ₹ 720$

Taxable cost of article = ₹ (4,000 - 720)

= ₹ 3,280

IGST = 18% of ₹ 3,280

$\Rightarrow \dfrac{18}{100} \times ₹ 3,280\\[1em] \Rightarrow \dfrac{9}{50} \times ₹ 3,280\\[1em] \Rightarrow ₹ \dfrac{29,520}{50}\\[1em] \Rightarrow ₹ 590.40$

Amount of bill = ₹ 3,280 + ₹ 590.40 = ₹ 3,870.40

Hence, the selling price of the bicycle = ₹ 3,870.40