Hey,
I just started looking into books for preparing for the GMAT and the book that was easily available for me was the "501 GMAT questions" by Learning Express. In their DS section i encountered two questions with solutions that make me doubt my and the authors understanding of the DS question format.
361 says: Is x divisible by five?
I. The sum of the digits is eight.
II. The first digit of x is 3.
Answer provided by the book: c. Both statements are needed together because if x is divisible by 5, the second digit must be either a zero or a 5. If the sum of the digits is 8, the only combination that would make x divisible by 5 would be 3 and 5 or 8 and 0. The second statement confirms that the first digit is 3, meaning the second digit has to be 5, so they can sum to 8.
I do not agree, since it is nowhere stated that x has two digits. 323 or 3122 etc. fulfill both statements and are not divisible by 5. In my understanding these statements are not sufficient, if they also allow for other X values.
362 says: Which company had a higher growth in net profit?
I. Company P’s net profits rose by 2.5%.
II. Company Q’s net profits rose by 3.7%.
Answer provided by the book: e. It does not matter how much the profits rose if we do not know the actual profits. 2.5% of 1,000 would be larger than 3.7% of 100.
Again, i have to disagree. "Growth" is in my definition always a relative measure, and in this case both statements together allow to make a comparison and answer the question. The case would be different if it would ask for the absolute change in net profit.
Which understanding of the DS question type corresponds more to the actual GMAT? Do I have to expect such ambiguity in the GMAT? Is this book of any use?
Best regards!