Shortcut Trick
CP of mixture = SP ÷ (100 + Profit%) × 100
CP of mixture = 48 ÷ 120 × 100 = ₹ 40 per kg
Ratio = (Cheaper Difference) : (Dearer Difference) = (40 − 32) : (45 − 40)
Ratio = 8 : 5
∴ The correct answer is 8 : 5.
Alternate Method
Given:
Price of Variety 1 (Dearer) = ₹ 45 per kg
Price of Variety 2 (Cheaper) = ₹ 32 per kg
Selling Price (SP) of mixture = ₹ 48 per kg
Profit percentage = 20%
Formula Used:
Cost Price (CP) = [SP × 100] / [100 + Profit%]
Alligation Rule: Quantity of Cheaper / Quantity of Dearer = (CP of Dearer − Mean Price) / (Mean Price − CP of Cheaper)
Calculations:
⇒ Mean CP = (48 × 100) / (100 + 20)
⇒ Mean CP = 4800 / 120 = ₹ 40
⇒ By Rule of Alligation:
⇒ Quantity of Bajra 1 : Quantity of Bajra 2 = (40 − 32) : (45 − 40)
⇒ Ratio = 8 : 5
∴ The correct answer is 8 : 5.
Additional Information
Rule of Alligation
It is used to find the ratio in which two ingredients at given prices must be mixed to produce a mixture of a specified mean price.
Mean Price Requirement
When applying alligation, all three values (Cheaper price, Dearer price, and Mean price) must be of the same unit, typically Cost Price (CP).
Profit and Loss Relation
If Selling Price (SP) and Profit% are given, always calculate CP first using CP = SP × [100 / (100 + P%)] before using the alligation cross.