A shopkeeper sells one transistor for Rs. 840 at a gain of 20% and another for Rs. 960 at a loss of 4%. His total gain or loss percent is:

Given Data

• Transistor 1: SP = Rs. 840 at 20% gain
• Transistor 2: SP = Rs. 960 at 4% loss
• Required: net percent gain or loss on both combined

Step 1: Compute individual cost prices (CP)
For 20% gain: SP = 1.20 × CP ⇒ CP₁ = 840 ÷ 1.20 = Rs. 700For 4% loss: SP = 0.96 × CP ⇒ CP₂ = 960 ÷ 0.96 = Rs. 1,000

Step 2: Aggregate CP and SP, then find net result
Total CP = 700 + 1,000 = Rs. 1,700Total SP = 840 + 960 = Rs. 1,800Net profit = 1,800 − 1,700 = Rs. 100Net profit% = (100 ÷ 1,700) × 100 ≈ 5.88% gain

Checks & Common Pitfalls

• Always evaluate combined profit by summing CPs and SPs, not by averaging percentages.
• Do not mix up loss base (CP) with SP when reversing loss.

Final Answer
Overall transaction results in a 5.88% gain.