GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 20 Oct 2018, 10:16

# Saturday Quant Quiz:

Starts promptly at 10 AM PST - Join in to Have Fun & Win Prizes

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# How many of the 400 students in the 11th grade will take calculus?

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 50007
How many of the 400 students in the 11th grade will take calculus?  [#permalink]

### Show Tags

27 Aug 2015, 01:16
00:00

Difficulty:

15% (low)

Question Stats:

80% (00:43) correct 20% (01:05) wrong based on 124 sessions

### HideShow timer Statistics

How many of the 400 students in the 11th grade will take calculus?

(1) 40 % of the students at the school take calculus.
(2) 80% of the 11th graders do not take calculus.

Kudos for a correct solution.

_________________
Manager
Joined: 14 Mar 2014
Posts: 147
GMAT 1: 710 Q50 V34
Re: How many of the 400 students in the 11th grade will take calculus?  [#permalink]

### Show Tags

27 Aug 2015, 03:34
Bunuel wrote:
How many of the 400 students in the 11th grade will take calculus?

(1) 40 % of the students at the school take calculus.
(2) 80% of the 11th graders do not take calculus.

Kudos for a correct solution.

IMO: B

St 1: 40% of the students at the school take calculus.

We don't know how many students are there in the school. Since only 11th grade students count is given.
Nt Suff

St 2: 80% of the 11th graders do not take calculus.

Thus remaining 20% 11th graders take calculus.
Suff
_________________

I'm happy, if I make math for you slightly clearer
And yes, I like kudos
¯\_(ツ)_/¯

Director
Joined: 21 May 2013
Posts: 651
Re: How many of the 400 students in the 11th grade will take calculus?  [#permalink]

### Show Tags

27 Aug 2015, 05:39
1
Bunuel wrote:
How many of the 400 students in the 11th grade will take calculus?

(1) 40 % of the students at the school take calculus.
(2) 80% of the 11th graders do not take calculus.

Kudos for a correct solution.

Statement 1: 40 % of the students at the school take calculus. Insufficient-We do not know how many students are there in the school.
Statement 2:80% of the 11th graders do not take calculus-This means 20% of 11th graders take calculus i.e 20% of 400 students. Sufficient
Manager
Joined: 13 Apr 2015
Posts: 74
Concentration: General Management, Strategy
GMAT 1: 620 Q47 V28
GPA: 3.25
WE: Project Management (Energy and Utilities)
Re: How many of the 400 students in the 11th grade will take calculus?  [#permalink]

### Show Tags

27 Aug 2015, 19:32
It should be E.

The statement does not tells that all 400 students should either take calculas or not. It 80% do not take calculus, the rest 20 could have also not taken calculus. They could have choosen some other topic.

Bunuel plz tell whether my approach to the question is right or not.

Manager
Joined: 26 Dec 2012
Posts: 146
Location: United States
Concentration: Technology, Social Entrepreneurship
WE: Information Technology (Computer Software)
Re: How many of the 400 students in the 11th grade will take calculus?  [#permalink]

### Show Tags

27 Aug 2015, 20:56
1
How many take calculus?
1. 40% of the take calculus, we don't know how many only took calculus as 40% may overlap total figure.insufficient
2. 80% did not take calculus, hence we know exactly 20 took calculus. sufficient.

Math Expert
Joined: 02 Sep 2009
Posts: 50007
Re: How many of the 400 students in the 11th grade will take calculus?  [#permalink]

### Show Tags

30 Aug 2015, 09:07
Bunuel wrote:
How many of the 400 students in the 11th grade will take calculus?

(1) 40 % of the students at the school take calculus.
(2) 80% of the 11th graders do not take calculus.

Kudos for a correct solution.

PRINCETON REVIEW OFFICIAL SOLUTION:

So, what are we looking at here? What do we need to find out?

The key words in this question are “How many”? We are looking to determine an exact value. If we were looking to do this as a multiple-choice question we would be well on the way to figuring this out. Let’s see, 40% of the school takes calculus, but I don’t know the total. How can I get the total? I can’t. What other information do I have? You would be embarking on a trip that you don’t need to go on.

This question requires you to determine a value. It would be the number of students taking calculus. Therefore, you must ask yourself whether the information given to you will get you to a value. YOU DO NOT NEED TO FIND THE VALUE.

Let’s look at the question. You are given the information that there are 400 students in the 11th grade. From this you should be thinking that if you knew how many weren’t taking it, or a percent of 11th graders that were or weren’t taking it, then you could get to the answer.

Moving to the information in number (1), 40% of the students at the school take calculus. Unfortunately, the 40% figure deals with the entire school population and you do not know anything about the individual distribution within grades. Not enough information to resolve. For those of you familiar with the AD/BCE split technology, at this point you would exclude both A and D as answer choices because (1) will not be sufficient. If we knew that it was 40% of every grade, then that would be a different story.

Moving to number (2), we see that 80% do not take calculus. We’re done at this point, and (B) is the right answer. But wait, we didn’t get the answer! Don’t waste your time to figure out the number. However for the sake of completeness, we would therefore know that 20% of the 11th graders took calculus. So, 400 x 20% = 80. This is a real answer that satisfies our requirement to know how many students in the 11th grade take calculus.

A couple of other points – be careful when you move from eliminating (1) and going to (2). When you do that, you must remind yourself that the information in (1) is currently not available. The only time to use both pieces of information is when neither works individually. You need to be really careful. This is the point when you must use both pieces of information to resolve whether you have enough to answer the question.

What have we learned today? It is important to be aware of the type of question you are working on and be able to put on the right thinking cap. You will need to be able to effortlessly glide between the different types of question. Therefore, as you are moving to the next question, pause for just a second to get a sense of the question and then attack!
_________________
Manager
Joined: 17 Jun 2015
Posts: 220
GMAT 1: 540 Q39 V26
GMAT 2: 680 Q46 V37
Re: How many of the 400 students in the 11th grade will take calculus?  [#permalink]

### Show Tags

22 Dec 2015, 12:31
Statment 1:

Statement 2:
80% do not take calculus
So, 20% do.

Sufficient

hence B
_________________

Fais de ta vie un rêve et d'un rêve une réalité

Director
Joined: 27 May 2012
Posts: 586
How many of the 400 students in the 11th grade will take calculus?  [#permalink]

### Show Tags

01 Nov 2017, 03:48
goldfinchmonster wrote:
It should be E.

The statement does not tells that all 400 students should either take calculas or not. It 80% do not take calculus, the rest 20 could have also not taken calculus. They could have choosen some other topic.

Bunuel plz tell whether my approach to the question is right or not.

: : : :

I somewhat had the same doubt .
let there be 100 people in 11 grade
80 do not take calculus. They take algebra.
remaining 20 take geometry
hence total 100 do not take calculus.

80 do not take calculus
20 take calculus
hence total 80 do not take calculus.

So B is insufficient.

Please feel free to point out any oversight from my part. Thank you.
_________________

- Stne

How many of the 400 students in the 11th grade will take calculus? &nbs [#permalink] 01 Nov 2017, 03:48
Display posts from previous: Sort by