8 kg of tea costing Rs 45 per kg is mixed with 12 kg costing Rs 30 per kg. What is the average price (in Rs per kg) of the mixture?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Rs 36
The average price is the total cost divided by the total weight.
Total cost \(=8\times45+12\times30=360+360=720\)
Total weight \(=8+12=20\) kg
Average \(=720\div20=36\)
The average price is Rs 36 per kg.
Why the other options are incorrect
Option (1) Rs 28.8 — Incorrect. This divides the total cost by 25 kg instead of 20 kg.
Option (2) Rs 37.5 — Incorrect. This is the plain average of the two prices; the quantities are not equal, so each price must be weighted by its quantity.
Option (4) Rs 39 — Incorrect. This weights each price by the other variety’s quantity.