Question

If two resistances are connected in series then its equivalent resistance is 45 ohm and if the same resistances are connected in parallel then its equivalent resistance is 10ohm .what are the values of these resistances

Answer 1

Rs=R1+R2=45

Rp=R1R2/R1+R2=10

R1R2=10R1+10R2

R1R2=10(R1+R2)

=10*45=450      (as R1+R2=45)

R1R2=450

R1(45-R1)=450

-R1²+45R1=450

R1²+450-45R1=0

R1²-30R1-15R1+450=0

(R1-30)(R1-15)=0

R1=30 or R1=15

therefore

R2=15 or R2=30 repectively.