Suman buys 40 kg of wheat at Rs.12.50/kg and 30 kg of wheat at Rs.14/kg. At what rate per kg should he sell the mixture to gain 5% on the whole?

Correct option is B

Given:
Wheat type 1 = 40 kg at Rs. 12.50 per kg
Wheat type 2 = 30 kg at Rs. 14 per kg
Gain = 5%
Formula Used:
Cost Price (CP) of mixture = Total cost ÷ Total quantity
Selling Price (SP) = CP × (1 + Gain%)
Solution:
Total cost of 40 kg wheat = 40 × 12.50 = Rs. 500
Total cost of 30 kg wheat = 30 × 14 = Rs. 420
Total cost = 500 + 420 = Rs. 920
Total quantity = 40 + 30 = 70 kg
Cost Price of mixture per kg =$$\frac {920}{70}$$​ = Rs. 13.14 (approx.)
Selling Price per kg = 13.14 × (1 + $$\frac{5}{100}$$​)
= 13.14 × 1.05 = Rs. 13.80 (approx.)