Source: Official Guide Revised GRE 1st Ed. Part 8; Section 5; #15
The total amount that Mary paid for
P P
I can figure out the upper limit but why is the lower limit $7?
Oct 11, 2018 • Comment
Sam Kinsman
Hi there,
Happy to help!
Think of it like this: what was the lowest possible cost of the book? In other words, what is the lowest possible value for (price of book + tax)?
Well, the person paid with $10, and got less than $3 change.
If the person had received EXACTLY $3 change, then the price (plus tax) would have been:
$10 - $3 = $7
But we know that the change was less than $3. Therefore the price (plus tax) must have been more than $7.
Does that make sense?
Oct 13, 2018 • Reply
Ishaan Tomar
Option A says that price of the book was less than 9.50. It doesn't say (as chris) the price has to be less than 9.50, so I think A should work. But obviosly its wrong. So how do we tackle this?
Aug 23, 2017 • Comment
Sam Kinsman
Hi Ishaan,
The question says "Which of the following statements must be true?" Option A says "the price of the book was LESS than $9.50." So if we can show that the price of the book could be $9.50, then we would prove that answer choice A is wrong (i.e. answer choice A does not have to be true).
As Chris showed, if the price of the book is $9.50, then the tax would be $0.38, and the total price would be $9.88. So Mary pays with $10, and gets 12 cents change. That fits what the question described (her change was less than $3.00). So the price of the book can be $9.50, and A is not correct.
I hope this helps!
Aug 26, 2017 • Reply
PRASHANT VERMA
Hey
i just went a much simple way that was forming the equation as the question says and then forming the range of price of book and tax:-
price of book 7< 1.04x <10
i just got stuck up at dividing 7 by 1.04 without using a calculator(i could have used but i tried all my effort to do it without a calculator but couldn't do it)??
Apr 13, 2017 • Comment
Cydney Seigerman, Magoosh Tutor
Hi Pawan :)
It looks like your inequality matches the information in the prompt:
7 < 1.04x
where x is the price of the book.
And if we plug in either $9.50 (to test A) or $6.90 (to test B), we can see that the book could be either of these prices and the inequality would hold true. Therefore, we can conclude that A and B do not necessarily have to be true.
On the other hand, we cannot use the inequality directly to test (C), which discusses the sales tax of the book and not the price of the book itself. For (C), the approach Chris goes over in the lesson video directly tests the sales tax, using the maximum possible value of the book as a starting point.
Apr 16, 2017 • Reply
Inmobi
I didn't really understand how option a and b are wrong, can you please explain?
Jun 7, 2016 • Comment
Cydney Seigerman, Magoosh Tutor
Hi Inmobi :)
I'm happy to help! Let's look at (A) and (B) to see why they're not correct :)
A. The price of the book was less than $9.50
If the book cost $9.50, then the sales tax would be 4% of this price or $0.38 (9.5*0.04). The total price of the book plus tax would be $9.88, in which case if Mary paid with a $10 bill, she would receive $0.18 back as change. This amount is less than $3, meeting the requirements of the question. In other words, the price of the book could be $9.50 and therefore does not have to be less than $9.50.
B. The price of the book was greater than $6.90.
To see if this statement must be true, let's consider when the price is equal to $6.90. In that case, the tax would be 4% of $6.90 or 27.6 cents. Let's round the cents up to 28 cents. So, the total cost of the book plus tax would be
$6.90 + $0.28 = $7.28
And if Mary paid with a $10 bill, she would receive $2.72 as change, which is less than $3. Therefore, the book could cost $6.90 and (B) is therefore not correct.
I hope this clears things up :)
Jun 10, 2016 • Reply
Qingxiang Jia
I am confused about the last option, which says the sales tax should be less than $0.45. But if we assume the maximum price is very close to $10 (which gives the maximum tax), the tax should be very close to $0.40, which is a tighter bound than the option C. So I concluded that option C is wrong too.
Aug 30, 2015 • Comment
Sam Kinsman
Hi Qingxiang, if the price of the book were $10, the sales tax would be $0.40. If the price of the book is lower than $10, the sales tax will be lower as well.
Mary paid with a $10 bill and got change, so the total cost of the book must be less than $10. Therefore, we know that the sales tax has to be lower than $0.40 - so we know option C is correct.
Oct 9, 2015 • Reply
chang feli
but option C is less than 0.45, then between 0.4 and 0.45, the condition is not valid. right?
Oct 25, 2018 • Reply
Adam
Hey Chang, we know for sure that the tax paid was less than $0.40. This means that it is most assuredly less than $0.45, no matter what. The sales tax is less than $0.45, and that is all that option C mentions. Thus, option C is true. It does not say anything about between $0.40 and $0.45, and since we know the tax is less than that, we don't have to think about that range at all.
Oct 29, 2018 • Reply
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