# A shopkeeper sells 1 pen for Rs. 10 on which he earns 100% profit. How many pens he should sell to gain profit of Rs. 650 ?

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A shopkeeper sells 1 pen for Rs. 10 on which he earns 100% profit. How many pens he should sell to gain profit of Rs. 650 ?
1. 65
2. 130
3. 260
4. 650

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Correct Answer - Option 2 : 130

Given

Shopkeeper pay per pen is Rs 10

Formula used

Profit = SP – CP,

Profit % = Profit/CP × 100,

Where,

SP is selling price,

CP is cost price,

Calculation

We have profit % = 100%,

⇒ 100 = (10 – CP/CP) × 100

⇒ CP = 10 – CP

⇒ 2CP = 10

⇒ CP = Rs. 5

Profit = 10 – 5 = Rs. 5

So he earns profit of Rs. 5 on one pen.

To gain Rs. 650,

⇒ 650/5 = 130

∴ He should sell 130 pens to gain profit of Rs. 650.