An ore contains 25% of an alloy that has 90% iron. Other than this, in remaining 75% of the ore ,there is no iron. How many kgs of the ore are needed to obtain 60 kg. of pure iron.?
250
275
300
266.66
Explanation:
Let us take 100x kgs of ore. Now it contains 25x kgs of alloy and it contains 90% (25x) kgs of iron.
90% (25x) = 60 kg => x = 60 × 10090 × 12560 × 10090 × 125 = 8383
So iron ore required = 100 × 8383 = 266.66