Answer:
Profit Percent= 20%.
Explanation:
Let's find how much the shopkeeper was charging for each book. For that, we divide the total amout of money earned by selling 4 books:
Rs 360/4 books= Rs 90/1 book., the books had a price of Rs 90/each.
Now, if he sells the remaining books (3 books) at the same price (Rs 90), he would be earning a total of Rs 90* 7= Rs 630.
To find his profit percent you can either divide the difference between total earnings and total costs by the total costs, or divide the difference of earnings of 1 book and the cost of 1 book by the cost of each book. Let's do it with the total amounts:
In this case, the 20% is a profit percent, because the earnings were a larger amount than the costs.