Can you generalize this?
1 ⋅ 3 1 + 1 ⋅ 3 ⋅ 5 2 + 1 ⋅ 3 ⋅ 5 ⋅ 7 3 + ⋯
If the sum above can be expressed as B A , where B is a prime and A is a positive integer, find ( A + B ) ! .
The answer is 6.
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1 solution
I really love ur 3 line solutions to summation problems! :)
Wow! This is beautiful!
Nice solution! Good work
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You just presented a dreadful but elegant way of writing the simplest fraction :P
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Yeah XD making people lose a little confidence
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@Shreyash Rai – Took it from FIITJEE's worksheet, lol:-)😁
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@Department 8 – Seemed like a fine question. Just curious what level would it be assigned
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@Shreyash Rai – OMG this is level 5 340 points!
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@Kaustubh Miglani – Ik right im shell shocked too
@Shreyash Rai – This CPP question is viral!
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@Kushagra Yadav – Its definetely rapidly gaining in popularity. That much is clear.
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@Shreyash Rai – Lvl 5 350!
@Shreyash Rai – Whats ur score in JSTSE mock test 4 ?reply fast
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@Kaustubh Miglani – im getting much lesser this time than approximately everyone near me. all you need to know is its below 140.
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@Shreyash Rai – Is it even below 130?Btw what was ur rank in mock test 1 and 2 Please reply
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@Kaustubh Miglani – Not below 130 10th in test 1 pretty bad in test 2 but why do you want to know My marks? It should be of no significance to you
@Kaustubh Miglani – What is your score? I'm getting 154
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@Kushagra Yadav – Its pretty much around ur score
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@Kaustubh Miglani – Tell me the number
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@Kushagra Yadav – Well its a little low,155-157.I am NOT SURE.Think i will come 1st?
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@Kaustubh Miglani – That's obvious
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@Kushagra Yadav – Nope it isnt,not at all.Well , I wanna be an expert in GK.Got some tips
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@Kaustubh Miglani – If all you guys are online check this .
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@Department 8 – I wont solve it.Well let it gain level first .Hahahaha
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@Kaustubh Miglani – So what is your answer?
@Kaustubh Miglani – are u sure u want me to post answer here?
@Kushagra Yadav – Ur score in real JSTSE is too good.My score is 174-175(not sure of 1 question) We will surely get close ranks.BTW,whats ur score in GK and SCience and maths individually?
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@Kaustubh Miglani – Damn why dont you do silly mistakes? How much dd you get in gk by the way?
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@Shreyash Rai – I do .I could have got 175-176 Tell ur marks and I will mine
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@Kaustubh Miglani – forget my marks. the official key is out by the way. you could check your marks nicely the link is http://www.edudel.nic.in/upload 2015 16/1782 dt 02022016.pdf
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@Shreyash Rai – Can u please send me the answer key ?Its not opening .Please Here is my email id nowiamachangedman@ gmail.com
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@Kaustubh Miglani – too lazy bro. well if you cant directly open the link then go to edudel.nic.in. then there would be an option called public circulars. under that you would see the ans key. if the site only doesnt open..........have fun
@Kaustubh Miglani – gk 33 phy 36 chem, bio 39 maths 27 what abut you??
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@Kushagra Yadav – gk 32 or 33 phy-34 sob sob sob chem-38 bio-40 maths-30 Think I CAN COME 1ST in delhi?
@Department 8 – Which phase?
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@Priyanshu Mishra – Our review classes are going on.
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@Department 8 – Wouldnt think that this ordinary cpp question would become lvl 5. Interesting it is.
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@Shreyash Rai – How many of your class could answer?
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@Swapnil Das – Actually I was the only one who answered. But then 2 or 3 Like lakshay I beleive May not have tried it
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@Shreyash Rai – My goodness, it's 335 points now.
Thanks
I'm amazed !!
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😋
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You live in ajmer ? I do !!
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@Akshat Sharda – You also ?? But your profile on Brilliant shows you are from Chandigarh...
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@Rishabh Jain – Yeah !! It is wrong !! I live in Ajmer and I'm in Mayoor School.
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@Akshat Sharda – 10 class ??
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@Rishabh Jain – Yes ! What about you ?
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@Akshat Sharda – I'm in 12th .
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@Rishabh Jain – You guys are in the same school?
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@Department 8 – Nope... Just the same city..... Ajmer :)
It has became HIGHLY over-rated . hardly a 150 point problem got a rating of 350 OMG!
400 points FIITJEE CPP problem! Its overrated man!
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i expected the question to be at lvl 3 or 4 at most. i was sooo wrong.
Lovely telescoping!
2 1 ( 1 ⋅ 3 3 − 1 + 1 ⋅ 3 ⋅ 5 5 − 1 + 1 ⋅ 3 ⋅ 5 ⋅ 7 7 − 1 + ⋯ ) = 2 1 ( ( 1 − 3 1 ) + ( 1 ⋅ 3 1 − 3 ⋅ 5 1 ) + ( 1 ⋅ 3 ⋅ 5 1 − 3 ⋅ 5 ⋅ 7 1 ) + ( 1 ⋅ 3 ⋅ 5 ⋅ 7 1 ⋯ ) = 2 1 × 1 = 2 1 ( 2 + 1 ) ! = 6