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 Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

A number when divided successively by 4 and 5 leaves [#permalink]

Show Tags

28 Aug 2012, 22:32

1

This post received KUDOS

3

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

65% (hard)

Question Stats:

42% (01:37) correct
58% (00:50) wrong based on 53 sessions

HideShow timer Statistics

A number when divided successively by 4 and 5 leaves remainder 1 and 4 respectively. when it is successively divided by 5 and 4, then the respective remainders will be;

A. 1,2 B. 2,3 C. 3,2 D. 4,1 E. Data not sufficient

Re: A number when divided successively by 4 and 5 leaves [#permalink]

Show Tags

29 Aug 2012, 01:12

7

This post received KUDOS

2

This post was BOOKMARKED

stne wrote:

A number when divided successively by 4 and 5 leaves remainder 1 and 4 respectively. when it is successively divided by 5 and 4, then the respective remainders will be;

A. 1,2 B. 2,3 C. 3,2 D. 4,1 E. Data not sufficient

When dividing a positive integer \(n\) by another positive integer \(D\) (divider), we obtain a quotient \(Q\), which is a non-negative integer and a remainder R, which is an integer such that \(0\leq{R}<D\). We can write \(n=DQ+R.\)

When dividing our number \(n\) by 4 we obtain a remainder of 1, so, if the quotient is some integer \(Q\), we can write \(n=4Q+1.\) Now, dividing \(Q\) by 5, we obtain another quotient say \(q\) and remainder 4, thus we can write \(Q=5q+4.\)

It follows that \(n=4(5q+4)+1=20q+17.\) Since \(n=20q+17=5(4q+3)+2\), it means that when dividing \(n\) by 5 first, we get a quotient \(4q+3\) and remainder 2. Then dividing \(4q+3\) by 4 we obviously obtain a remainder of 3.

Answer B. _________________

PhD in Applied Mathematics Love GMAT Quant questions and running.

Re: A number when divided successively by 4 and 5 leaves [#permalink]

Show Tags

29 Aug 2012, 22:09

EvaJager wrote:

stne wrote:

A number when divided successively by 4 and 5 leaves remainder 1 and 4 respectively. when it is successively divided by 5 and 4, then the respective remainders will be;

A. 1,2 B. 2,3 C. 3,2 D. 4,1 E. Data not sufficient

When dividing a positive integer \(n\) by another positive integer \(D\) (divider), we obtain a quotient \(Q\), which is a non-negative integer and a remainder R, which is an integer such that \(0\leq{R}<D\). We can write \(n=DQ+R.\)

When dividing our number \(n\) by 4 we obtain a remainder of 1, so, if the quotient is some integer \(Q\), we can write \(n=4Q+1.\) Now, dividing \(Q\) by 5, we obtain another quotient say \(q\) and remainder 4, thus we can write \(Q=5q+4.\)

It follows that \(n=4(5q+4)+1=20q+17.\) Since \(n=20q+17=5(4q+3)+2\), it means that when dividing \(n\) by 5 first, we get a quotient \(4q+3\) and remainder 2. Then dividing \(4q+3\) by 4 we obviously obtain a remainder of 3.

Answer B.

Thanks for the solution eva ..+1 _________________

Re: A number when divided successively by 4 and 5 leaves [#permalink]

Show Tags

29 Aug 2012, 22:25

1

This post received KUDOS

Expert's post

1

This post was BOOKMARKED

stne wrote:

A number when divided successively by 4 and 5 leaves remainder 1 and 4 respectively. when it is successively divided by 5 and 4, then the respective remainders will be;

A. 1,2 B. 2,3 C. 3,2 D. 4,1 E. Data not sufficient

You can solve it by checking for a number.

What do you mean by 'divided successively by 4 and 5'? It means, you divide the number by 4 and then you divide the quotient obtained (and not the original number) by 5.

When divided by 4, the number leaves remainder 1 so the number must be of the form 5 or 9 or 13 or 17 or 21 etc. For each of these numbers, remainder will be 1 and quotient will be 1 or 2 or 3 or 4 or 5 respectively. When the quotient obtained is divided by 5, it leaves remainder 4. We can easily pin point this number if the quotient obtained is 4 itself. The remainder will be 4 in that case. Hence 17 satisfies the given condition.

When you divide 17 by 5, you get 2 remainder and 3 quotient. When you divide 3 by 4, you get 3 remainder.

Answer (B)

Note: GMAT PS questions do not have 'data not sufficient' option. _________________

Re: A number when divided successively by 4 and 5 leaves [#permalink]

Show Tags

30 Aug 2012, 00:41

VeritasPrepKarishma wrote:

stne wrote:

A number when divided successively by 4 and 5 leaves remainder 1 and 4 respectively. when it is successively divided by 5 and 4, then the respective remainders will be;

A. 1,2 B. 2,3 C. 3,2 D. 4,1 E. Data not sufficient

You can solve it by checking for a number.

What do you mean by 'divided successively by 4 and 5'? It means, you divide the number by 4 and then you divide the quotient obtained (and not the original number) by 5.

When divided by 4, the number leaves remainder 1 so the number must be of the form 5 or 9 or 13 or 17 or 21 etc. For each of these numbers, remainder will be 1 and quotient will be 1 or 2 or 3 or 4 or 5 respectively. When the quotient obtained is divided by 5, it leaves remainder 4. We can easily pin point this number if the quotient obtained is 4 itself. The remainder will be 4 in that case. Hence 17 satisfies the given condition.

When you divide 17 by 5, you get 2 remainder and 3 quotient. When you divide 3 by 4, you get 3 remainder.

Answer (B)

Note: GMAT PS questions do not have 'data not sufficient' option.

Maybe, it would have been better to replace E by "Cannot be determined". In fact, this question can be easily transformed into a DS question:

What is the value of positive integer n?

(1) When divided by 4, n leaves a reminder of 1. (2) After dividing n by 4, the quotient is further divided by 5 leaving a remainder of 4. _________________

PhD in Applied Mathematics Love GMAT Quant questions and running.

Re: A number when divided successively by 4 and 5 leaves [#permalink]

Show Tags

31 Aug 2012, 16:25

EvaJager wrote:

VeritasPrepKarishma wrote:

stne wrote:

A number when divided successively by 4 and 5 leaves remainder 1 and 4 respectively. when it is successively divided by 5 and 4, then the respective remainders will be;

A. 1,2 B. 2,3 C. 3,2 D. 4,1 E. Data not sufficient

You can solve it by checking for a number.

What do you mean by 'divided successively by 4 and 5'? It means, you divide the number by 4 and then you divide the quotient obtained (and not the original number) by 5.

When divided by 4, the number leaves remainder 1 so the number must be of the form 5 or 9 or 13 or 17 or 21 etc. For each of these numbers, remainder will be 1 and quotient will be 1 or 2 or 3 or 4 or 5 respectively. When the quotient obtained is divided by 5, it leaves remainder 4. We can easily pin point this number if the quotient obtained is 4 itself. The remainder will be 4 in that case. Hence 17 satisfies the given condition.

When you divide 17 by 5, you get 2 remainder and 3 quotient. When you divide 3 by 4, you get 3 remainder.

Answer (B)

Note: GMAT PS questions do not have 'data not sufficient' option.

Maybe, it would have been better to replace E by "Cannot be determined". In fact, this question can be easily transformed into a DS question:

What is the value of positive integer n?

(1) When divided by 4, n leaves a reminder of 1. (2) After dividing n by 4, the quotient is further divided by 5 leaving a remainder of 4.

Thank you eva and karishma

here is a matrix way which I found here, no need to search for a number by trial and error directly obtain the number that is being divided (successively). By this method.

(i)arrange both the divisors in ascending order , and their respective remainders below it a b c d

(ii)next cross multiply diagonally like this d * a (iii)and then add c this will give the number that is being divided ,( dividend )

so coming back to the given question we have a=4 , b = 5 , c= 1 and d = 4

4 5 1 4

so 4*4 +1 = 17 the original number we are dividing ( dividend )

17/4 = quotient 4 and remainder 1 ( as stated ) quotient 4 divided by 5 remainder 4 ( as stated )

so this must be the number as it meets both the conditions , now that we know the number it becomes relatively easy.

Now the question becomes when 17 is divided successively by 5 and 4 what are the remainders ?

now 17/5 = quotient 3 remainder 2

quotient 3 divided by 4 remainder 3 , hence when 17 is divided successively by 5 and 4 , the remainders are 2 and 3 , and that is required answer. answer = (B) _________________

Re: A number when divided successively by 4 and 5 leaves [#permalink]

Show Tags

02 Sep 2012, 22:18

Expert's post

stne wrote:

Thank you eva and karishma

here is a matrix way which I found here, no need to search for a number by trial and error directly obtain the number that is being divided (successively). By this method.

(i)arrange both the divisors in ascending order , and their respective remainders below it a b c d

(ii)next cross multiply diagonally like this d * a (iii)and then add c this will give the number that is being divided ,( dividend )

so coming back to the given question we have a=4 , b = 5 , c= 1 and d = 4

4 5 1 4

so 4*4 +1 = 17 the original number we are dividing ( dividend )

17/4 = quotient 4 and remainder 1 ( as stated ) quotient 4 divided by 5 remainder 4 ( as stated )

so this must be the number as it meets both the conditions , now that we know the number it becomes relatively easy.

Now the question becomes when 17 is divided successively by 5 and 4 what are the remainders ?

now 17/5 = quotient 3 remainder 2

quotient 3 divided by 4 remainder 3 , hence when 17 is divided successively by 5 and 4 , the remainders are 2 and 3 , and that is required answer. answer = (B)

The 'matrix method' is exactly the same as the other methods. It is just a different representation. There is nothing wrong with it but can you really 'learn' a different method for every type of question you come across? If you can, go ahead. There is absolutely nothing wrong with it.

The matrix method is finding the first number.

If we put n in the equation form using a, b, c and d (as used in the matrix method by you), we get n = a(bm + d) + c = 4(5m + 4) + 1 [as shown by EvaJager above] Here, to get the first value of n, you are just assuming m = 0. You get n = ad + c = 4*4 + 1 (this is what your matrix method does) I also did the same to get the value of 17. I assumed that the quotient when you divide by 5 is 0 and all you have to worry about is the remainder of 4. So you just have to obtain the quotient as 4 in the previous step.

As I said, the method is no different and there is nothing wrong with it. If you do want to use it, make sure you understand why you are multiplying a and d together and then adding c. _________________

Re: A number when divided successively by 4 and 5 leaves [#permalink]

Show Tags

17 Oct 2012, 03:42

Can the matrix method suggested by stne also be used in the case where we are dividing the number three times?

For example:

On dividing a certain number by 5,7,8 successively, the remainders are 2,3 and 4 respectively. What would be the remainders if order of division is reversed.

Re: A number when divided successively by 4 and 5 leaves [#permalink]

Show Tags

17 Oct 2012, 04:34

karishmasparmar wrote:

Can the matrix method suggested by stne also be used in the case where we are dividing the number three times?

For example:

On dividing a certain number by 5,7,8 successively, the remainders are 2,3 and 4 respectively. What would be the remainders if order of division is reversed.

(1) I don't think such a question can appear on the real GMAT test. (2) I don't know how the method proposed by stne would work in this case. Even the algebra can get quite messy... \(n=5(7(8N+4)+3)+2=5\cdot{7}\cdot{8}N+157\), for some positive integer \(N\). In reverse order, when dividing by 8,7,5 successively, first quotient \(5\cdot{7}N+19\) and remainder 5. Then, dividing by 7, quotient \(5N+3\) and remainder 4. Finally, when dividing by 5, quotient \(N\) and remainder 3. _________________

PhD in Applied Mathematics Love GMAT Quant questions and running.

Re: A number when divided successively by 4 and 5 leaves [#permalink]

Show Tags

17 Oct 2012, 21:28

1

This post received KUDOS

Expert's post

karishmasparmar wrote:

Can the matrix method suggested by stne also be used in the case where we are dividing the number three times?

For example:

On dividing a certain number by 5,7,8 successively, the remainders are 2,3 and 4 respectively. What would be the remainders if order of division is reversed.

Most certainly! As I said in my post before, the matrix method is just another representation of algebra/logic. Finally you are doing the same thing in every case.

Divisors: a, b, c Remainders: m, n, p

a b c m n p

Use matrix method twice: First focus on two right columns: you get b*p + n. Then multiply this result i.e. (b*p + n) by a and add m to it to get a*(b*p + n) + m

To look at your example: 5 7 8 2 3 4

First step: 7*4 + 3 = 31 Second step 5*31 + 2 = 157

157 is the first such number. Divide 157 by 8, 7, 5 in that order: 157/8 Quotient = 19, Remainder = 5 19/7 Quotient = 2, Remainder = 5 2/5 Quotient = 0, Remainder = 2

Remainders are 5, 5, 2

But preferably, don't use this method. Just use logic. Why? Because, say, you knew this 'matrix method' and used it to solve 2 divisor problems. What if you get 3 divisor problems in the test? Can you use matrix method at that time? No! I derived the method for 3 divisor problems by first working out the logic and then putting it in the matrix form. So why not use logic only?

Think this way:

Divisors: 5, 7, 8 Remainders: 2, 3, 4

You start by considering the last step first. At the end, when you divide by 8, you want remainder to be 4 (let's assume the quotient we get is 0 in this case). This means that after division by 7, we should get 4 as the quotient (so that we can get 4 as remainder when we divide by 8 in the next step). So, when you divide by 7, the quotient must be 4 and remainder must be 3. At this step, the number must be 7*4 + 3 = 31 Now, when you divide by 5, you need the quotient to be 31 and remainder to be 2 so number must be 5*31 + 2 = 157 157 is the first such number. (If this is not very clear, divide 157 successively by 5, 7, and 8 and see what goes on).

Now you proceed as before!

I hope you see that you can follow the same logic and solve even with 5 or more divisors very quickly!

Also, there is nothing wrong with 'such a question'. It's very logical and hence fair game as far as GMAT is concerned. _________________

Excellent posts dLo saw your blog too..!! Man .. you have got some writing skills. And Just to make an argument = You had such an amazing resume ; i am glad...

So Much $$$ Business school costs a lot. This is obvious, whether you are a full-ride scholarship student or are paying fully out-of-pocket. Aside from the (constantly rising)...

They say you get better at doing something by doing it. then doing it again ... and again ... and again, and you keep doing it until one day you look...

I barely remember taking decent rest in the last 60 hours. It’s been relentless with submissions, birthday celebration, exams, vacating the flat, meeting people before leaving and of...