Solution :-
Selling price of the watch = Rs. 448
Profit earned = 12 %
Cost price = ?
Let the cost price of the watch be Rs. 'x' .
Then according to the question.
⇒ x/1 + (x*12)/100 = 448
Taking L.C.M. of the denominators and then solving it.
⇒ (100x + 12x)/100 = 448
⇒ 112x = 448*100
⇒ x = 44800/112
⇒ x = Rs. 400
So, the cost price of the watch is Rs. 400
Now, we have to find the profit % if the selling price is Rs. 512
Selling price - Cost price = Profit
Profit = 512 - 400
Profit = Rs. 112
Profit % = (Profit*100)/Cost Price
⇒ (112*100)/400
⇒ 11200/400
⇒ 28 %
So, if the selling price of the watch is Rs. 512, then the profit is 28 % Answer .