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.
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:
Are you attending an MBA or Masters program outside in the US or Europe and wondering how to finance your studies? In this exclusive conversation, we discuss the collateral-free non-cosigner education loans...
Solve 30 high quality GMAT Focus practice questions in timed conditions. Take this GMAT practise test live with peers, analyze your GMAT study progress, and see where you stand in the GMAT student pool.
Join us in a comprehensive talk about the F1 Student Visa process with Travis Feuerbacher, former U.S. Visa Officer and licensed U.S. immigration attorney having expertise working for the U.S. Department of State
Ready to skyrocket your career with an MBA? Get ahead with our curated list of FREE courses and resources to kickstart your journey into business education!
For more than a decade, Target Test Prep has been helping GMAT students clear seemingly impossible hurdles and achieve MASSIVE score increases on test day. Our students prove time and time again that there is no “ceiling”...
Do RC/MSR passages scare you? e-GMAT is conducting a masterclass to help you learn – Learn effective reading strategies, Tackle difficult RC & MSR with confidence, and Excel in timed test environment
Join us for an exclusive one-day event focused on mastering the GMAT and maximizing your preparation resources! Here's what you can expect: Don't miss out on this invaluable opportunity to supercharge your GMAT preparation journey.
Simple and quick divisibility test for 7
[#permalink]
06 Feb 2013, 00:27
Here is something that I found while scratching my head and looking for the rules of divisibility for the number -7.
Let's do it by example a) 2695 -Multiply the number of hundreds the number has by 2. 2695 = 2600 + 95 So, 26*2 = 52
-Add the remaining two digit number. Here the remaining two digit number is 95 Hence, 52+95 = 147
- Check whether the resulting sum is divisible by 7. if yes, then the original number is divisible by 7. 147/7 = integer Therefore, 2695 is divisible by 7
Another example: b) 26957
Step 1 => 26900 + 57 Therefore, 269*2 = 538
Step 2 => 538 + 57 = 595
Step 3 => Check if 595/7 is an integer. Indeed, 595/7 = 85 Thus, 26957 is divisible by 7.
This in my opinion is the fastest way to check the divisibility of a number by 7.
I'd be glad to see some appreciation in the form of Kudos. :wink:
Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Actually looks a little tedious. 269*2, 595/7 , 538+57 one of these may be the exact point where things may go wrong.
I follow a similar stratgey but with simple calculations involving 0s. It may or may not help others. Take out huge chunks from calculations that are multiple of 7. get help of 0s as much as possible
Such as, 28957 28000 is multiple of 7, so need to check only for 957 700 is multiple of 7, so need to check only for 257 210 is multiple of 7, so need to check only for 47 and we know the ans.
Actually looks a little tedious. 269*2, 595/7 , 538+57 one of these may be the exact point where things may go wrong.
I follow a similar stratgey but with simple calculations involving 0s. It may or may not help others. Take out huge chunks from calculations that are multiple of 7. get help of 0s as much as possible
Such as, 28957 28000 is multiple of 7, so need to check only for 957 700 is multiple of 7, so need to check only for 257 210 is multiple of 7, so need to check only for 47 and we know the ans.
Hope it helps
You changed the number from 26957 to 28957, was it intentional? When the thousandth digits are multiple of 7 then, I'd go with your suggestion. I like it. However, when its not, as is the case here (26957), What will you do? 21000+5957 ? => 5600+357 => 350 + 7 => 7...!
Hmmm, it may take same amount of time. I guess its a matter of preference. However, I like the suggestion. Will keep in mind.
Re: Simple and quick divisibility test for 7
[#permalink]
06 Feb 2013, 01:02
Vishwa25 wrote:
You changed the number from 26957 to 28957, was it intentional? When the thousandth digits are multiple of 7 then, I'd go with your suggestion. I like it. However, when its not, as is the case here (26957), What will you do? 21000+5957 ? => 5600+357 => 350 + 7 => 7...!
Hmmm, it may take same amount of time. I guess its a matter of preference. However, I like the suggestion. Will keep in mind.
Intentional, to show the calculations.
Quote:
However, when its not, as is the case here (26957), What will you do?
you can take your number: 26957 21000 is multiple of 7, so need to check only for 5957 5600 is multiple of 7, so need to check only for 357 350 is multiple of 7, so need to check only for 7 and we know the ans.
Re: Simple and quick divisibility test for 7
[#permalink]
31 Aug 2013, 11:06
Actually all the above methods were cool but lenthy(ingleesh prowblem :-D ) i derived something which is really easy and sort if you memorize given numbers....
I found a method which if you keep in mind it will make little faster..... keep in mind these number right digit->left digit 1->2(i.e double) 2->4(i.e double) 3->6(i.e double) 4->1(i.e 1 greater than 3 so 4-3=1) 5->2(i.e 2 greater than 3 so 5-3=2) 6->5(i just muggup this number )
how you going to memorize these is up to you now if the unit digit is one of them the right handside digit should be according to that else subtract it. here is the example 1) to check 7203 the right hand digit is 3 so the left hand side digit must be 6 but here it is not so subtract 6 from 0 the remaining number(i.e 714) is divisible by 7 let's check it the last digit is now 4 so the previous digit should be 1 and it is now remains 7 which is already divisible by 7
2) to check 509796 the right hand digit is 6 to the left hand side digit must be 5 but it is 9 (oh i forgot to say if the digit is greater than 7 you can also subtract 7 from it so 9 became 2) now subtract 5 from it, it remains 4. now the left hand side number is divisible by 7, let's check now th number(which is actually 50974) has it's last digit 4 so the previous digit should be 1 but here it's not so subtract 1 from 7 it became 6 now the previous digit should be 5 but it is 9 so subtract 5 from 9 now the number(which is actually 504) has it's last digit 4 so the previous digit should be 1 but here it's again not so subtract 1 from 0 which gives 49 which is divisible by 7
Actually it's very easy if you remember the Process/Method
Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
gmatclubot
Re: Simple and quick divisibility test for 7 [#permalink]