Question

Two resistances R1 and R2 have a combined
resistance of 4.5 ohms when in series and 1 ohm when
in parallel. The resistances R1 and R2 are:
(1) 3 and 6 ohms
(2) 3 and 9 ohms
(3) 1.5 and 3 ohms
(4) 1.5 and 0.5 ohms

Answer 1

HEYA....

option 3 is correct

series=> R1+R2=1.5+3=4.5ohm

parallel=>1/R1 +1/R2

=1/1.5+1/3

=15/15

=1ohm

HOPE THIS HELPS...

Answer 2

in series,

R₁ + R₂ = 4.5 Ω --------------------(1)

in parallel,

$\frac{R_{1}\times{R_{2}} }{R_{1}+R_{2}  } = 1 ohm$

⇒ $\frac{R_{1}\times{R_{2}}  }{4.5}=1\\ R_{1}=\frac{4.5}{R_{2} }$

putting value of R₁ in eqn 1

$4.5+R_{2} ^{2}-4.5R_{2}=0$

on solving we get

R₁ = 1.5 Ω or 3 Ω

R₂ = 3 Ω or 1.5 Ω

your ans is (3)