Question 17

If a person sold his watch for Rs.24 with a profit percentage numerically equal to its cost price, then the cost price of the watch is Rs.

Solution

Let say cost price is c.

So, profit percentage=c%.

Selling price=c(1+c/100).

So,

c(1+c/100)=24.

or,$$c^2+100c-2400=0$$

or,$$c^2+120c-20c-2400=0$$

or,$$c(c+120)-20(c+120)=0$$

or,(c+120)(c-20)=0.

so,either c=-120 or c=20.

Cost price cannot be negative value.

so, c =20.

C is correct choice.

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