A discount of 15% on one article is the same as a discount of 20% on another article. Find the cost price of the two articles.

A 15% discount on one article = 20% discount on another article.

15% of Cost Price of Article 1=20% of Cost Price of Article 2

​$$15\% \text{ of Cost Price of Article 1} = 20\% \text{ of Cost Price of Article 2} \\ \ \\ 0.15 \times \text{CP}_1 = 0.20 \times \text{CP}_2 \\ \ \\\frac{\text{CP}_1}{\text{CP}_2} = \frac{0.20}{0.15} = \frac{20}{15} = \frac{4}{3}$$​​

Thus,  $$\text{CP}_1 : \text{CP}_2 = 4 : 3$$​​

Now, Checking the Options for the Ratio 4 : 3

Option A: Rs. 80 and Rs. 60 → 80 : 60 = 4 : 3

Option B: Rs. 70 and Rs. 50 → 70 : 50 = 7 : 5 $$\neq$$​ 4 : 3 

Option C: Rs. 40 and Rs. 20 → 40 : 20 = 2 : 1 $$\neq$$​ 4 : 3 

Option D: Rs. 60 and Rs. 40 → 60 : 40 = 3 : 2 $$\neq$$​ 4 : 3

Therefore, The correct option is A: Rs. 80, Rs. 60.