Profit and Loss — The ratio of Cost Price (CP) to Selling Price (SP) is 3:7. If SP is ₹ 700, determine the CP.

Introduction / Context:
Ratio questions become trivial if you map the ratio parts to real values using a single unit multiplier.

Given Data / Assumptions:

• CP : SP = 3 : 7
• SP = ₹ 700

Concept / Approach:
Let each part be k. Then CP = 3k and SP = 7k. Given SP = 700 ⇒ 7k = 700 ⇒ k = 100 ⇒ CP = 3k = 300.

Step-by-Step Solution:

Verification / Alternative check:
Profit% = (SP − CP)/CP * 100 = (700 − 300)/300 * 100 = 133.33% (not needed, but confirms ratio mapping).

Why Other Options Are Wrong:
₹ 400, ₹ 500, ₹ 800, and ₹ 350 do not satisfy the fixed 3:7 mapping with SP = ₹ 700.

Common Pitfalls:
Misplacing the ratio (taking CP : SP as 7 : 3) or dividing the wrong value by the wrong part.

Final Answer:
₹ 300