A shopkeeper in Indore sells 20 identical articles for ₹ 450 each. Find the amount of bill if he gives 20% discount and then charges GST = 28%

Selling price of 1 article = ₹ 450

Selling price of 20 articles = ₹ 450 x 20

= ₹ 9,000

Discount = 20% of ₹ 9,000

$\Rightarrow\dfrac{20}{100} \times ₹ 9,000\\[1em] \Rightarrow\dfrac{1}{5} \times ₹ 9,000\\[1em] \Rightarrow ₹ \dfrac{9,000}{5}\\[1em] \Rightarrow ₹ 1,800$

Taxable cost of articles = ₹ 9,000 - ₹ 1,800

= ₹ 7,200

IGST = 28% of ₹ 7,200.

$\Rightarrow \dfrac{28}{100} \times ₹ 7,200\\[1em] \Rightarrow \dfrac{7}{25} \times ₹ 7,200\\[1em] \Rightarrow ₹ \dfrac{50,400}{25}\\[1em] \Rightarrow ₹ 2,016$

Amount of bill = ₹ 7,200 + ₹ 2,016

= ₹ 9,216

Hence, amount of bill = ₹ 9,216.