Equal-expenditure purchases: A person spends ₹36 at each of five markets, where prices per orange are ₹1.00, ₹1.50, ₹1.80, ₹2.00, and ₹2.25. Find the average price per orange across all oranges bought.
Correct Answer: ₹ 1.58
Introduction / Context:When spending equal amounts at different prices, the number of items purchased varies inversely with price. The overall average price equals (total spent) / (total items), which simplifies using reciprocals of the prices (a harmonic-mean style setup weighted by equal expenditure).
Given Data / Assumptions:
- Spend per market = ₹36 (five markets)
- Prices: ₹1.00, ₹1.50, ₹1.80, ₹2.00, ₹2.25 per orange
Concept / Approach:Total oranges = Σ(36 / price). Total spend = 5 * 36. Average price = (total spend) / (total oranges) = 5 / Σ(1 / price).
Step-by-Step Solution:
Σ(1/price) = 1/1 + 1/1.5 + 1/1.8 + 1/2 + 1/2.25= 1 + 0.666666... + 0.555555... + 0.5 + 0.444444... = 19/6Average price = 5 / (19/6) = 30/19 = ₹1.5789... ≈ ₹1.58Verification / Alternative check:Compute total oranges explicitly: 36, 24, 20, 18, 16 → total 114 oranges for ₹180 → 180/114 = ₹1.5789..., same result.
Why Other Options Are Wrong:
- ₹1.91, ₹2.00, ₹1.80, ₹1.70: do not equal 30/19 to two decimal places.
Common Pitfalls:Averaging prices directly (arithmetic mean) without accounting for different quantities obtained at each price due to equal spending.
Final Answer:₹ 1.58