By selling 90 ball pens for Rs 160 a person loses 20%. How many ball pens should be sold for Rs 96 so as to have a profit of 20%?

Explanation

To solve the problem step-by-step, we will first determine the cost price of one ball pen and then calculate how many ball pens need to be sold for Rs 96 to achieve a profit of 20%.

### Step 1: Determine the Cost Price of One Ball Pen
Given that selling 90 ball pens for Rs 160 results in a loss of 20%, we can set up the following equation:

1. Let the cost price of one ball pen be \( X \).
2. The cost price of 90 ball pens will be \( 90X \).
3. The selling price of 90 ball pens is Rs 160.
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