Question

3 resistors of 9 ohm are given.How will you connect them to get a net resistance of a) 13.5 ohm b) 6 ohm?

Answer 1

a) one will in series and 2 will be parrale...
so,
total resistance will be 1/9+1/9=2/9
so resistace will be 9/2=4.5
now total resultant resustance will be 4.5+9=13.5

b) 2 will be in series and both will be parallel ro third one.. so that,
9+9 =18
and 1/18+1/9= 3/18= 1/6
so resistance will be 6ohm

Answer 2

if you connect 2 of them in parallel, you will get 4.5 ohm.
now if you connect the remaining in series, you will get effective as 13.5ohm.
Now if you reverse the order ,i.e. 2 in series and one in parallel you will get it as 6 ohm.