Mixture average price and total gain Alok mixes 25 kg at Rs 6/kg with 35 kg at Rs 7/kg and sells the 60 kg mixture at Rs 6.75/kg. What is the overall gain or loss?

Introduction / Context:
When mixing two lots sold as a single mixture, compute the weighted-average cost price and compare with the selling price. Multiply the per-kg margin by total kg to get total gain or loss.

Given Data / Assumptions:

• Lot 1: 25 kg at Rs 6/kg.
• Lot 2: 35 kg at Rs 7/kg.
• Mixture sold at Rs 6.75/kg; total quantity = 60 kg.

Concept / Approach:
Average CP = (Total cost) / (Total kg). Gain per kg = SP - Avg CP. Total gain = gain per kg × total kg.

Step-by-Step Solution:
Total cost = 25 × 6 + 35 × 7 = 150 + 245 = 395.Average CP = 395 / 60 ≈ 6.5833.SP = 6.75 ⇒ Gain per kg ≈ 0.1667.Total gain ≈ 0.1667 × 60 = 10.

Verification / Alternative check:
Direct difference method confirms: (SP − CP_avg) × 60 = (6.75 − 395/60) × 60 = 10.

Why Other Options Are Wrong:
Rs 16 gain/loss and Rs 20 gain do not follow from the computed average and margin.

Common Pitfalls:
Using simple average of prices ( (6 + 7)/2 ) instead of weighted average by quantities.

Final Answer:
Rs 10.00 gain