CP of 10 pens equals SP of 8 — Aptitude Question
CP of 10 pens equals SP of 8: If the cost price of 10 pens equals the selling price of 8 pens, what is the profit… Answer and worked solution on CodeKairo.
- Topic: Profit & Loss
- Section: Quantitative Aptitude
- Difficulty: Medium
- Time target: 60 seconds
Question
If the cost price of 10 pens equals the selling price of 8 pens, what is the profit percent?
Options
- 20%
- 25%
- 30%
- 40%
Show the answer and the worked solution
Correct answer: B. 25%
Worked solution
- Let CP per pen = ₹1. Then 8 pens sell for ₹10, so SP per pen = ₹1.25.
- Profit = 25%.
Answer: 25%.
The idea
The (b − a)/a rule again, with b = 10 and a = 8. Pricing one unit at 1 makes every question of this shape identical.
Shortcut. Per pen, SP : CP = 10 : 8 = 5 : 4, so each pen sells for a quarter more than it costs — 25%.
Common trap. 20% — dividing the 2-pen difference by 10 instead of by the 8 pens sold.