Q. 125.0( 1 Vote )
Mark the correct A. 1
B. 3
C. 8
D. none of these
Answer :
Let say GP is
a,ar,ar2
where a is the first term and r is the common ratio
Also, given that r = 2
So, GP becomes
a,2a,4a
nth term = ar(n-1) = 128
a.2(n-1) = 128
⇒ 
⇒ a.2n = 256
Sum of n terms of GP
⇒ 
⇒ 
⇒ 
Substituting a2n in above equation we get
-255 = a-256
a =1.
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