Store S sold a total of 90 copies of a certain book

[Ladan]

What is the approach to solving questions similar to the one below?

Thanks for all your explanations!

[Ladan]

I forgot to mention that the correct answer is B.

[Guest]

Statement (2): The store sold 38 copies on Saturday. So in the rest of the 6 days combined, it sold 52 copies. We need to find out whether we can express 52 as the sum of 6 distinct numbers (no two days had the same sales as per the question) with one of them greater than 11.

In order for us to express 52 as a sum of 6 distinct integers, one of the numbers has to be greater than 11. Because if you start with 11, the largest 6 distinct number combination we can have is:

11 + 10 + 9 + 8 + 7 + 6 = 51.

But 12 + 10 + 9 + 8 + 7 + 6 = 52

Since the question says Friday has the 2nd greatest sales, the largest number in the 6 number combo will be the Friday sales which is greater than 11.

SUFFICIENT.

Statement (1): It says Thursday had a sales of 8 copies. By applying the same logic, in Statement (2), we may be able to find 6 distinct numbers that makes 82, but it is not sufficient to tell whether Friday sales will be greater than 11.

NOT SUFFICIENT.

[StaceyKoprince]

Nice, guest

Remember in a yes / no DS question, you want to see if you can make a statement give you both a yes and a no, in which case it is insufficient. As guest points out, for statement 2, we can only find a value for Friday that is 12 or greater. For statement 1, let me elaborate just a little:

Th = 8, so remaining days combined = 82.

I could have 25 + 20 + 15 + 10 + 8 + 4 = 82, in which case Friday = 20. That gives me a "yes."
I could also have 50 + 10 + 8 + 6 + 5 + 3 = 82, in which case Friday = 10. That gives me a "no."

A yes and a no = insufficient.