Radha bought a watch for Rs. 144 and got a percentage of profit equal to the cost price of the watch. What is the cost price of the watch?	Choose one.
A) Rs. 72
B) Rs. 78
C) Rs. 80
D) Rs. 90
E) Rs. 92
SP=144   CP=x   profit %=x   C.P.= (100/(100+gain%))*S.P.   x=(100/100+x) *144   x^2+100x=14400   x^2+180x-80x-14400=0   (x+180) (x-80)=0   x=-180   x=80   ANSWER:Rs. 90
<result>D</result>
Radha bought a watch for Rs. 144 and got a percentage of profit equal to the cost price of the watch. What is the cost price of the watch?