Hi C Okigbo
This question comes down to how you choose to organize your work and do the math - and there ARE several different ways to go about it. The individual "steps" involved aren't that tough, but you really have to stay organized to work through this question efficiently.
To start, we're given a "recipe" for making orange juice: 1 can of concentrate + 3 cans of water = 4 CANS of juice
Next, we're told that each "can" = 12 ounces. Combined with the prior info (above)....
1 can of concentrate + 3 cans of water = 4 cans of juice = 48 OUNCES of juice
We're told to make 200 6-ounce servings of juice, which is 200(6) = 1,200 ounces of juice. The question asks how many cans of CONCENTRATE are needed to get us 1,200 ounces (according to the recipe).
Since 1 can of concentrate --> 48 ounces of juice, we can do division to figure out the number of cans needed:
1200/48 = 25 cans of concentrate
Final Answer: A
As I mentioned earlier, there are a number of different ways to "do the math" on this question (and you can even TEST THE ANSWERS), so I'm sure that there will be other approaches mentioned by other posters.
GMAT assassins aren't born, they're made,
Rich