IIT JEE , AIEEE Forum - Mathematics , Algebra

umang

Find the largest term common in sequences 1,11,21,31,41,..... to 100 terms and 31,36,41,46,51,56,.... to 100 terms ????????

saarika

is the answer 521???

umang

Hey !

actually , it aws an objective question . and the answer given is 471 . Pls explain how u got ur answer !!!!!

saarika

in the first series 1,11.... the 100th term is 991 (by the formula Tn=a+(n-1)d)

in the second series31,36,41............100th term is 526.

first series is 1,11..........521.......991

second series is 31,36..........516,521,526

hence the largest common term is 521.

is there any mistake in my solution?? please let me know..

saarika

reply soon!!!!!!

unavailable

common differences of first series= 10

common differences of second series= 5

first common term = 41

if you observe closely

there will be a sequence for common terms with common difference 10*5=50

hence the sequence will be

41, 91, 141, 191 .....................

as saarika found it last terms of the two sequences are 991,and 526.

take the minimum one

i.e 526

41+(n-1)50=526

n=10.7

n is a integer so n=10

putting in the formula

t₁₀= 491

i think 471 is not the answer as it does not satisfy the equation

if 491 in the option!!!!

please verify

unavailable · 03/03/2007 22:52 Subject: Re:common term

03/03/2007 22:52 Subject: Re:common term

common differences of first series= 10 common differences of second series= 5 first common term = 31 if you observe closely there will be a sequence for common terms with common difference 10 hence the sequence will be 31,41,51..................... as saarika found it last terms of the two sequences are 991,and 526. take the minimum one i.e 526 31+(n-1)10=526 n=50.5 n is a integer so n=50 putting in the formula t₁₀= 521 sorrrrrrrrrrrrry!!!!!!!!! 521 is right saarika is right ignore the first post

magiclko

521 will be the answer,

see it can be solved logically also, the first series's numbers ranging frm [1,526) all will be also of that of the other series, so defintely 521 will be the answer,

hey umang,hav u taken this question frm fiitjee package??? its given thr also as 471... but the answer is defintely 521!!!

rajat

hey ,the answer is 521.bcoz 521 occurs in both the series which is of course >471

i do not care what the book says bcoz if u can see it with ur eyes that it is 521,why should we say that we are wrong and the book is right ????

umang

Hey shashank !!

yes , ur solution is correct .

And sarika ,you hav applied hit and trial method , though ur answer is correct. I dont know why the book says the answer=471 , but yes , 521 must be the correct answer !!!!!!!

Ask & Discuss Questions with Community & Experts