Difficulty: Easy
Correct Answer: Rs. 60
Explanation:
Introduction / Context: This is a classic two-condition percentage problem. One sale gives a loss percentage; a slightly higher selling price flips the outcome to a stated gain percentage. The difference between the two selling prices allows direct recovery of the cost price (CP).
Given Data / Assumptions:
Concept / Approach: Subtract the two expressions to isolate CP. The 35% spread between −25% and +10% corresponds to the ₹ 21 difference in selling price, yielding CP directly by division.
Step-by-Step Solution:
SP2 − SP1 = (1.10 − 0.75) * CP = 0.35 * CP Given SP2 − SP1 = 21 ⇒ 0.35 * CP = 21 CP = 21 / 0.35 = 60 Hence, CP = ₹ 60Verification / Alternative check: SP1 = 0.75 * 60 = 45; SP2 = 1.10 * 60 = 66; difference = 21 (matches).
Why Other Options Are Wrong: 56, 84, and 92 do not satisfy a 35% spread of ₹ 21. 72 yields SP1 = 54 and SP2 = 79.2 (difference 25.2), not 21.
Common Pitfalls: Adding 25% and 10% to SP instead of to CP, or misreading the ₹ 21 increment as percentage instead of an absolute rupee change.
Final Answer: Rs. 60
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