Combination of combination
Consider all 6-digit numbers of the form abccba where b is odd. Determine the number of all such 6-digit numbers that are divisible by 7.
The answer is 70.
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1 solution
this was my prmo problem today and i did it. How was your prmo bro?
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how was yours
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i think i will qualify since i had qualified last year. i have done 10 sums correct without any calculation mistake. did you do the red and blue colouring sum?what was your answer?
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@Alekhya China – @ALEKHYA CHINA Hello!!! I also gave prmo.......Well that questions answer came out to be 90.....It can be solved by simple symmetry..........How was your paper??
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@Aaghaz Mahajan – MYpaper was no so good i gave prmo first time can u know the expected cutoff of prmo for up region.......
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@Anshaj Shukla – Hello!!! Well see, the previous year cutoff was based on the number of questions solved, not the marks.............so I dont really know abt this year........But I guess it might be around 30 marks or something....... Btw I am from UP region too......!!
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@Aaghaz Mahajan – how was your marks....!
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@Anshaj Shukla – Well..........You see I never calculate my marks.....I'm just gonna wait for the results......But What about you?? How was the experience??
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@Aaghaz Mahajan – not so much good
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@Anshaj Shukla – i qualified yup FIRST TIME
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@Anshaj Shukla – Thats nice!!!! Congratulations!!!!
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@Aaghaz Mahajan – hey how do i prepare for RMO
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@Anshaj Shukla – Spend a lot of time on Brilliant, and bu some books as suggested on the HBSCE website............Also, see this
https://brilliant.org/tags/rmo/
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@Aaghaz Mahajan – does functional equation come in rmo
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@Anshaj Shukla – Yup it can come.........
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@Aaghaz Mahajan – what is Gerry Myerson's clever inequality?
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@Anshaj Shukla – Ummm.......I dont really know......Never even heard of it......!!!
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@Aaghaz Mahajan – i saw a question a person solve 3 pages solution in 7 steps by this inequality
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@Anshaj Shukla – hey does php comes in rmo
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@Anshaj Shukla – Ummm.......look it may come.....there isnt any well defined syllabus.......JUST do whatever you can do........!! Php can be used to solve certain problems so theres no harm in reading it......
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@Aaghaz Mahajan – aaghaz can u tell me what is the previous year cutoff for rmo uttar pradesh and delhi
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@Anshaj Shukla – Yaa bro.....it was 29 marks last year in UP region........How are your preparations going??
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@Aaghaz Mahajan – worst my school half yearly is going on my parents saying more focus on half yearly because rmo is held every year
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@Anshaj Shukla – Mann!!!! Listen.......I believe that RMO is much more important, so Focus on that!!!
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@Aaghaz Mahajan – rmo is much imp can my parents understand it!!!!
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@Anshaj Shukla – No problems bro....just abhi ke liye chill and prepare.......kal ke liye Best of luck...... and exams ki tayaari na rmo ke baad karna kal..........!!
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@Aaghaz Mahajan – BEST OF LUCK BRO I GIVE RMO IN CLASS 11 WITH FULL PREPARATION. BEST OF LUCK AGAIN
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@Anshaj Shukla – hey how was ur paper
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@Anshaj Shukla – paper is very tough
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@Anshaj Shukla – Well.........mera to sahi gaya thaa...........I mean, I got arn 3-4 correct............What abt you???
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@Aaghaz Mahajan – But tera to first time thaa naa........isliye no problem.........!!!! Try nexxt time if this wasnt so good!!!
@Anshaj Shukla – You can prepare for half yearlys later on.........I mean why spend time on them!!!!
@Anshaj Shukla – I am appearing fr RMO too..........Gotta prep up now!!
i did blunders yeserday... In second question i have same answer(7.64) but i take it 7 but answer is 8 next 23 my answer is correct 14.98 but i think if i do 14 that create lot difference so i do 15 but it was incorrect.... Similarly i lost 16 marks......
abccba (b is odd) = a(105 + 1) + b(104+ 10) + c(103+ 102) = a (1001 – 1) 100 + a + 10b(1001) + (100) (11) c = (7.11.13.100)a – 99a + 10b(7.11.13) + (98 + 2)(11)c = 7p + (c – a) where p is an integer Now if c – a is a multiple of 7 c – a = 7, 0, –7 Hence number of ordered pairs of (a, c) is 14 since b is odd Number of such number = 14 × 5 = 70