An ore contains 25% of an alloy that has 90% iron. Other than this, in the remaining 75% of the ore, there is no iron. How many kilograms of the ore are needed to obtain 60 kg of pure iron?  Pick one.
A) 250 kg	B) 275 kg	C) 300 kg	D) 266.66 kg	E) None
Solution: Let there is 100 kg of ore.   25% ore contains 90% off Iron that means 25 kg contains;    25*90/100= 
<gadget id="calculator"> 25*90/100</gadget>
<output>45/2 = around 22.5</output>
22.5 kg Iron.   22.5 kg Iron contains 100 kg of ore.   Then, 1 kg of iron contains= 25/100 kg ore;   Hence, 60 kg iron contains = 100*60/22.5 = 266.66 kg ore.   Answer: Option 266.66 kg
<result>D</result>
An ore contains 25% of an alloy that has 90% iron. Other than this, in the remaining 75% of the ore, there is no iron. How many kilograms of the ore are needed to obtain 60 kg of pure iron?