1i think n=13 is the ans.
does it match with ur ans?
let 3 nos are removed from the set{2,22,23,24,.......2n}
the GM of remaining nos is 237/5.........find the value of n
partially a doubt :P
want to confirm the ans
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8 Answers
1yeah.....i was getting 13 only..
can someone complete this one.....
open to all...
1we have to deal with AM of exponents
suppose 2a, 2b, 2c are removed from the set
n(n+1)2 - (a+b+c) = 375(n-3)
since LHS is an integer RHS is also an integer, so n is of the form 5k+3 where k is a positive integer
now, 1+2+3 ≤ a+b+c ≤ n-2 + n-1 + n........using this and n = 5k+3
6 ≤ (5k+3)(5k+4)2 - 37k ≤ 5k+3-2 + 5k+3-1 + 5k+3
25k2 - 69k ≤ 0, 25k2 - 39k ≥ 0
from these two : k = 2, so n = 5k+3 = 13
this solution u can say is a by-product of one of Hari sir's solution :)
