Hello!
I tried solving the question and the solution comes out to be option (c) 125/64 .
I am explaining the solution below:-
S = 1+ (3/5)+ (6/5^2)+ (10/5^3)+ (15/5^4)+......
=>S/5 = (1/5)+ (3/5^2)+ (6/5^3)+ (10/5^4)+.....
=>4S/5= (1/5)+ (2/5)+ (3/5^2)+ (4/5^3)+ (5/5^3)+....
=>4S/5^2= (1/5)+ (2/5^2)+ (3/5^3)+ (4/5^3)+....
We can take,
(4S/5) - (4S/25)= 1+ (1/5)+ (1/5^2)+ (1/5^3)+.....
=>(16S/25)= 1+ (1/5)+ (1/5^2)+......[Infinite G.P]
We have, a=1 and r=(1/5).
So, S=a/(1-r) =1/(1-1/5) = 1/(4/5)
=>16S/25= 5/4 => S= 125/64.
Hope this cleared your confusion!
Happy learning:)
Question : Directions: Select the option in which the numbers share the same relationship in the set as that shared by the numbers in the given set. (NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into their constituent digits. E.g.13 – operations on 13 such as adding/subtracting/multiplying etc. to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed) (32, 24, 8) (48, 42, 6)
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