Two resistances R1=300±2% and R2=600±1% are connected in parallel. The effective resistance in ohm is

Here ∆R1R1=2100 and ∆R2R2=1100  R=R1R2R1+R2=300×600900=200 As 1R=1R1+1R2  Differentiating∆RR2=∆R1R12+∆R2R22 and∆RR1R=∆R1R11R1+∆R2R21R2∆RR1200=21001300+11001600∆RR12=5600    ∆RR×100=53%