Profit and Loss — A sells an article to B at a 10% profit, and B sells it to C at a 10% loss. If C pays ₹ 2079, how much did A originally pay (A’s cost price)?

Introduction / Context:
Successive percentage changes applied to the same base (the item) can be chained multiplicatively. Here, a +10% followed by −10% yields a net factor of 0.99 applied to A’s cost when reaching C’s payment amount.

Given Data / Assumptions:

• A’s cost = x (unknown).
• A → B at +10% ⇒ B’s cost = 1.10x.
• B → C at −10% ⇒ C’s payment = 0.90 * (1.10x) = 0.99x.
• C pays ₹ 2079.

Concept / Approach:
Equate 0.99x to 2079 and solve for x. This is a straightforward reverse-percentage problem using multiplicative chaining.

Step-by-Step Solution:

Verification / Alternative check:
Forward chain: 2100 * 1.10 = 2310; 2310 * 0.90 = 2079 (matches C’s payment).

Why Other Options Are Wrong:
2160 or 2400 would map through the 0.99 net factor to values different from 2079; 2480 and 2000 are arbitrary here.

Common Pitfalls:
Treating +10% and −10% as canceling to 0%; multiplicative chaining shows the net factor is 0.99, not 1.00.

Final Answer:
₹ 2100