Scaling a combined purchase (pens and pencils): The total cost of 36 pens and 42 pencils is ₹460. What is the cost of 18 pens and 21 pencils at the same unit prices?

Introduction / Context:
Because the basket (18 pens, 21 pencils) is exactly half of (36 pens, 42 pencils), the total cost scales linearly by the same factor when unit prices remain constant.

Given Data / Assumptions:

• Cost(36 pens + 42 pencils) = ₹460
• Unit prices fixed; no discounts or bulk changes
• Target: 18 pens + 21 pencils (half of both counts)

Concept / Approach:
Linear scaling applies: if quantities are halved, the total cost is halved.

Step-by-Step Solution:
Target basket = 1/2 of the original basketCost = 1/2 * ₹460 = ₹230

Verification / Alternative check:
Let pen price be p and pencil price be q. Then 36p + 42q = 460. For 18p + 21q, exactly half: (36p + 42q)/2 = 230.

Why Other Options Are Wrong:
₹203, ₹302, ₹320, ₹240 do not match the linear scaling by 1/2 of the original total cost.

Common Pitfalls:
Overthinking and trying to solve for p and q individually; not needed when the target combination is a fixed scalar multiple.

Final Answer:
₹230/-