Yesterday, Manhattan GMAT posted a GMAT question on our blog. Today, they have followed up with the answer:
Since each cucumber is 99% water by weight, each one is also 1% something else (say, “mush.”) So each cucumber is 99% water and 1% mush. That means that all the cucumbers together are 99% water and 1% mush. Since the total weight is 100 pounds, the weight of the mush is equal to 0.01(100) = 1 pound, and the weight of the water is 99 pounds.
After the water evaporates, each cucumber is 98% water. Therefore, we know that all the cucumbers together are 2% mush and 98% water. The key point is that the amount of water changed, but the amount of mush has not. Thus, we should equate the amount of mush BEFORE with the amount of mush AFTER.
If we call the new, unknown weight of the cucumbers x, then the weight of the mush after evaporation is 2% of x, or 0.02x.
Now, we can equate the weight of the mush before and after:
1 pound = 0.02x
1/0.02 = x
50 = x
The new weight of the bag is 50 pounds.
The correct answer is B.