A wrist watch is sold for Rs.1,200 at a profit per cent equal to its cost price. Find the cost
price of the wrist watch.

SP/CP = CP*((100+CP)%) +CP /CP
when SP=1200, above relation only satisfies when CP is kept 300.

Let the cost price (CP) of the wrist watch be Rs. x.
Given, selling price (SP) of the wrist watch = Rs. 1200.
Profit per cent = CP = x.
Therefore, SP = CP + Profit
i. e., SP = x + x% of x
i. e., 1200 = x + (x/100) * x
i. e., x = 300
Hence, the cost price of the wrist watch is Rs. 300.

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