Correct Answer - Option 4 : 125

**Given:**

The cost price of 150 pens is equal to the selling price of a certain number of pens.

The profit is 20%.

**Formula used:**

Profit or Gain = Selling price – Cost Price

Loss = Cost Price – Selling Price

Profit percentage = (Profit /Cost Price) × 100

Loss percentage = (Loss / Cost price) × 100

**Calculation: **

Let the number of pens sold be x.

CP of 150 = SP of x

Let CP of one pen be Rs. 10.

SP = Rs. (1.2 × 10) = Rs. 12

CP of 10 = SP of x

⇒ 150 × 10 = 12 × x

⇒ x = 125

**∴ required number of pens sold is 125**